Category: Class 11

Subject Matter Experts at SamacheerKalvi.Guide have created Tamil Nadu State Board Samacheer Kalvi 11th Books Answers Solutions Guide Pdf Free Download in English Medium and Tamil Medium are part of Samacheer Kalvi Books Solutions.

Let us look at these TN State Board New Syllabus Samacheer Kalvi 11th Std Guide Pdf of Text Book Back Questions and Answers of Volume 1 and Volume 2, Chapter Wise Important Questions, Study Material, Question Bank, Notes, Formulas and revise our understanding of the subject.

Students can also read Tamil Nadu Samacheer Kalvi 11th Model Question Papers 2020-2021.

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TN Samacheer Kalvi 11th Book Back Answers Solutions Guide

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Subject Matter Experts at SamacheerKalvi.Guide have created Samacheer Kalvi Tamil Nadu State Board Syllabus New Paper Pattern 11th Accountancy Model Question Papers 2020-2021 with Answers Pdf Free Download in English Medium and Tamil Medium of TN 11th Standard Accountancy Public Exam Question Papers Answer Key, New Paper Pattern of HSC 11th Class Accountancy Previous Year Question Papers, Plus One +1 Accountancy Model Sample Papers are part of Tamil Nadu 11th Model Question Papers.

Let us look at these Government of Tamil Nadu State Board 11th Accountancy Model Question Papers Tamil Medium with Answers 2020-21 Pdf. Students can view or download the Class 11th Accountancy New Model Question Papers 2021 Tamil Nadu English Medium Pdf for their upcoming Tamil Nadu HSC Board Exams. Students can also read Tamilnadu Samcheer Kalvi 11th Accountancy Guide.

TN State Board 11th Accountancy Model Question Papers 2020 2021 English Tamil Medium

Tamil Nadu 11th Accountancy Model Question Papers English Medium 2020-2021

• Tamil Nadu 11th Accountancy Model Question Paper 1 English Medium
• Tamil Nadu 11th Accountancy Model Question Paper 2 English Medium
• Tamil Nadu 11th Accountancy Model Question Paper 3 English Medium
• Tamil Nadu 11th Accountancy Model Question Paper 4 English Medium
• Tamil Nadu 11th Accountancy Model Question Paper 5 English Medium

Tamil Nadu 11th Accountancy Model Question Papers Tamil Medium 2020-2021

• Tamil Nadu 11th Accountancy Model Question Paper 1 Tamil Medium
• Tamil Nadu 11th Accountancy Model Question Paper 2 Tamil Medium
• Tamil Nadu 11th Accountancy Model Question Paper 3 Tamil Medium
• Tamil Nadu 11th Accountancy Model Question Paper 4 Tamil Medium
• Tamil Nadu 11th Accountancy Model Question Paper 5 Tamil Medium

11th Accountancy Model Question Paper Design 2020-2021 Tamil Nadu

Types of Questions	Marks	No. of Questions to be Answered	Total Marks
Part-I Objective Type	1	20	20
Part-II Very Short Answers (Totally 10 questions will be given. Answer any Seven. Any one question should be answered compulsorily)	2	7	14
Part-Ill Short Answers (Totally 10 questions will be given. Answer any Seven. Any one question should be answered compulsorily)	3	7	21
Part-IV Essay Type	5	7	35
Marks			90
Internal Assessment			10
Total Marks			100

Tamil Nadu 11th Accountancy Model Question Paper Weightage of Marks

Purpose	Weightage
1. Knowledge	30%
2. Understanding	40%
3. Application	20%
4. Skill/Creativity	10%

It is necessary that students will understand the new pattern and style of Model Question Papers of 11th Standard Accountancy Tamilnadu State Board Syllabus according to the latest exam pattern. These Tamil Nadu Plus One 11th Accountancy Model Question Papers State Board Tamil Medium and English Medium are useful to understand the pattern of questions asked in the board exam. Know about the important concepts to be prepared for TN HSLC Board Exams and Score More marks.

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Let us know if you have any concerns regarding the Tamil Nadu Government 11th Accountancy State Board Model Question Papers with Answers 2020 21, TN 11th Std Accountancy Public Exam Question Papers with Answer Key, New Paper Pattern of HSC Class 11th Accountancy Previous Year Question Papers, Plus One +1 Accountancy Model Sample Papers, drop a comment below and we will get back to you as soon as possible.

Tamilnadu State Board New Syllabus Samacheer Kalvi 11th Chemistry Guide Pdf Chapter 15 Environmental Chemistry Text Book Back Questions and Answers, Notes.

Tamilnadu Samacheer Kalvi 11th Chemistry Solutions Chapter 15 Environmental Chemistry

11th Chemistry Guide Environmental Chemistry Text Book Back Questions and Answers

Textbook Evaluation:

I. Choose the best answer:

Question 1.
The gaseous envelope around the earth is known as atmosphere. The region lying between an altitudes of 11 – 50 km is _______.
(a) Troposphere
(b) Mesosphere
(c) Thermosphere
(d) Stratosphere
Answer:
(d) Stratosphere

Question 2.
Which of the following belongs to secondary air pollutant?
(a) Hydrocarbon
(b) Peroxy acetyl nitrate
(c) Carbon monoxide
(d) Nitric oxide
Answer:
(a) Hydrocarbon

Question 3.
Which of the following is natural and human disturbance in ecology?
(a) Forest fire
(b) Floods
(c) Acid rain
(d) Green house effect
Answer:
(b) Floods

Question 4.
Bhopal Gas Tragedy is a case of _______.
(a) thermal pollution
(b) air pollution
(c) nuclear pollution
(d) land pollution
Answer:
(c) nuclear pollution

Question 5.
Haemoglobin of the blood forms carboxy haemoglobin with
(a) Carbon dioxide
(b) Carbon tetra chloride
(c) Carbon monoxide
(d) Carbonic acid
Answer:
(c) Carbon monoxide

Question 6.
Which sequence for green house gases is based on GWP?
(a) CFC > N₂O > CO₂ > CH₄
(b) CFC > CO₂ > N₂O > CH₄
(c) CFC > N₂O > CH₄ > CO₂
(d) CFC > CH₄ > N₂O > CO₂
Answer:
(b) CFC > CO₂ > N₂O > CH₄

Question 7.
Photo chemical smog formed in congested metropolitan cities mainly consists of
(a) Ozone, SO₂ and hydrocarbons
(b) Ozone, PAN and NO₂
(c) PAN, smoke and SO₂
(d) Hydrocarbons, SO₂ and CO₂
Answer:
(d) Hydrocarbons, SO₂ and CO₂

Question 8.
The pH of normal rain water is
(a) 6.5
(b) 7.5
(c) 5.6
(d) 4.6
Answer:
(c) 5.6

Question 9.
Ozone depletion will cause
(a) forest fires
(b) eutrophication
(c) bio magnification
(d) global warming
Answer:
(a) forest fires

Question 10.
_______ is considered to be ozone friendly substitude for CFC’S
(a) HFC (Hydro Fluro Carbon)
(b) Halons
(c) PAN (Peroxy acetyl nitrate)
(d) PAH (Poly cyclic aromatic hydro carbon)
Answer:
(d) PAH (Poly cyclic aromatic hydro carbon)

Question 11.
Identify the wrong statement in the following.
(a) The clean water would have a BOD value of less than 5 ppm
(b) Greenhouse effect is also called as Global warming
(c) Minute solid particles in air is known as particulate pollutants
(d) Biosphere is the protective blanket of gases surrounding the earth
Answer:
(c) Minute solid particles in air is known as particulate pollutants

Question 12.
Living in the atmosphere of CO is dangerous because it
(a) combines with O₂ present inside to form CO₂
(b) Reduces organic matter of tissues
(c) Combines with haemoglobin and makes it incapable to absorb oxygen
(d) Dries up the blood
Answer:
(c) Combines with haemoglobin and makes it incapable to absorb oxygen

Question 13.
World Ozone layer protection Day is celebrated in ________.
(a) June 5
(b) Nov – 19
(c) Sep – 16
(d) Jan – 26
Answer:
(c) Sep – 16

Question 14.
Release of oxides of nitrogen and hydrocarbons into the atmosphere by motor vehicles is prevented by using
(a) grit chamber
(b) scrubbers
(c) trickling filters
(d) catalytic convertors
Answer:
(b) scrubbers

Question 15.
Biochemical oxygen Demand value less than 5 ppm indicates a water sample to be
(a) highly polluted
(b) poor in dissolved oxygen
(c) rich in dissolved oxygen
(d) low COD
Answer:
(d) low COD

Question 16.
Match the List I with List II and select the correct answer using the code given below the lists:

List I	List II
A. Depletion of ozone layer	1. CO2
B. Acid rain	2. NO
C. Photochemical smog	3. SO2
D. Green house effect	4. CFC

Code:

Answer:
(a)

Question 17.
Match the List I with List II and select the correct answer using the code given below the lists.

List I	List II
A. Stone leprosy	1. CO
B. Biological magnification	2. Green house gases
C. Global warming	3. Acid rain
D. Combination with haemoglobin	4. DDT

Code:

Answer:
(d)

Question 18.
Assertion (A):
If BOD level of water in a reservoir is more than 5 pm it is highly polluted.
Reason (R):
High biological oxygen demand means high activity of bacteria in water.
(i) Both (A) and (R) are correct and (R) is the correct explanation of (A)
(ii) Both (A) and (R) are correct and (R) is not the correct explanation of (A)
(iii) Both (A) and (R) are not correct
(iv) (A) is correct but (R) is not correct
(a) i
(b) ii
(c) iii
(d) iv
Answer:
(a) i

Question 19.
Assertion (A):
Excessive use of chlorinated pesticide causes soil and water pollution.
Reason (R):
Such pesticides are non – biodegradable.
(i) Both (A) and (R) are correct and (R) is the correct explanation of (A)
(ii) Both (A) and (R) are correct and (R) is not the correct explanation of (A)
(iii) Both (A) and (R) are not correct
(iv) (A) is correct but (R) is not correct
(a) i
(b) ii
(c) iii
(d) iv
Answer:
(a) i

Question 20.
Assertion (A):
Oxygen plays a key role in the troposphere
Reason (R):
Troposphere is not responsible for all biological activities
(i) Both (A) and (R) are correct and (R) is the correct explanation of (A)
(ii) Both (A) and (R) are correct and (R) is not the correct explanation of (A)
(iii) Both (A) and (R) are not correct
(iv) (A) is correct but (R) is not correct
(a) i
(b) ii
(c) iii
(d) iv
Answer:
(b) ii

II. Write brief answer to the following questions:

Question 21.
Dissolved oxygen in water is responsible for aquatic life. What processes are responsible for the reduction in dissolved oxygen in water?
Answer:
The process which are responsible for the reduction of dissolved oxygen in water are excessive use of phosphatic and nitrate fertilizers, detergents, the discharge of human sewage and organic waste from food, paper and pulp industries. The microorganisms which oxidize organic matter also used oxygen dissolved in H₂O.

More over, during night, photosynthesis stops but the aquatic plants continue to respire, resulting in reduction of dissolved oxygen.

Question 22.
What would happen, if the greenhouse gases were totally missing in the earth’s atmosphere?
Answer:
The solar energy radiated back from the earth surface in absorbed by the green house gases. (CO₂, CH₄, O₃, CFCs) are present near the earth’s surface. They heat up the atmosphere near the earth’s surface and keep it warm.

As a result of these, there is growth of vegetation which supports the life. In the absence of this effect, there will be not life of both plant and animal on the surface of the earth.

Question 23.
Define smog.
Answer:
Smog is a combination of smoke and fog which forms droplets that remain suspended in the air. Smog is a chemical mixture of gases that forms a brownish yellow haze over urban cities.Smog mainly consists of ground level ozone, oxides of nitrogen, volatile organic compounds, SO₂ acidic aerosols and gases, and particulate matter.

Question 24.
Which is considered to be earth’s protective umbrella? Why?
Answer:
At high altitudes to the atmosphere consists of a layer of ozone (O₃) which acts as an umbrella or shield for harmful UV radiations. It protects us from harmful effect such as skin cancer. UV radiation can convert molecular oxygen into ozone as shown in the following reaction.
O₂(g) O(g) + O(g)
O(g) + O₂(g) O₃(g)

Question 25.
What are degradable and non – degradable pollutants?
Answer:
The pollutants are classified as bio-degradable and non-biodegradable pollutants.

Bio-degradable pollutants:
The pollutants which can be easily decomposed by the natural biological processes are called bio-degradable pollutants.
Example:
plant wastes, animal wastes etc.

Non bio-degradable pollutants:
The pollutants which cannot be decomposed by the natural biological processes are called Non bio-degradable
pollutants.
Examples:
Metal wastes (mainly Hg and Pb), D.D.T, plastics, nuclear wastes etc.,
These pollutants are harmful to living organisms even in low concentration. As they are not degraded naturally, it is difficult to eliminate them from our environment.

Question 26.
From where does ozone come in the photo chemical smog?
Answer:
NO₂ NO + (O)
O₃ are strong oxidizing agent and can react with unburnt hydrocarbons in polluted air to form formaldehyde, acrolein and peroxy acetyl nitrate (PAN).

Question 27.
A person was using water supplied by corporation. Due to shortage of water he started using underground water. He felt laxative effect. What could be the cause?
Answer:
A moderate concentration of sulphate ions in water are harmless but excessive concentration is greater than 500 ppm in water causes laxative effects. Hence under ground water may have consisted excess of suplhates.

Question 28.
What is green chemistry?
Answer:
Efforts to control environmental pollution resulted in development of science for synthesis of chemicals favorable to environment which is called green chemistry. Green chemistry means science of environmentally favorable chemical synthesis.

Question 29.
Explain how does green house effect cause global warming.
Answer:
Greenhouse effect may be defined as the heating up of the earth surface due to trapping of infrared radiations reflected by earth’s surface by CO₂ layer in the atmosphere”. The heating up of earth through the greenhouse effect is called global warming.

Without the heating caused by the greenhouse effect, Earth’s average surface temperature would be only about -18 °C (CPF). Although the greenhouse effect is a naturally occurring phenomenon, it is intensified by the continuous emission of greenhouse gases into the atmosphere.

During the past 100 years, the amount of carbon dioxide in the atmosphere increased by roughly 30 percent and the amount of methane more than doubled. If these trends continue, the average global temperature will increase which can lead to melting of polar ice caps and flooding of low lying areas. This will increase incidence of infectious diseases like dengue, malaria etc.

Question 30.
Mention the standards prescribed by BIS for quality of drinking water.
Answer:
Standard characteristics prescribed for deciding the quality of drinking water by BIS, in 1991 are shown in Table.

Question 31.
How does classical smog differ from photochemical smog?
Answer:
Classical smog was first observed in London in December 1952 and hence it is also known as Londo coal smoke and fog.

It occurs in cool atmospheric smog found in many large cities. The chemical composition is the mixture of SO₂, SO₃ and humidity. It generally occurs in the morning and becomes worse when the sun rises. This is mainly due to the induced oxidation of SO₂ to SO₃, which reacts with water yielding sulphuric acid aerosol.

Chemically it is reducing in nature because of high concentration of SO₂ and so it is also called as reducing smog.

ii) Photo chemical smog or Los Angel Smog:
Photo Chemical smog was first observed in Los Angels in 1950. It occurs in warm, dry and sunny climate. This type of smog is formed by the combination of smoke, dust and fog with air pollutants like oxides of nitrogen and hydrocarbons in the presence of sunlight.

It forms when the sun shines and becomes worse in the afternoon. Chemically it is oxidizing in nature because of high concentration of oxidizing agents NO₂ and O₃, so it is also called as oxidizing smog.

Question 32.
What are particulate pollutants? Explain any three.
Answer:
1. Particulate pollutants are small solid particles and liquid droplets suspended in air. Many of particulate pollutants are hazardous.
Examples: dust, pollen, smoke, soot and liquid droplets (aerosols) etc,

2. Smoke particulate consists of solid particles (or) mixture of solid and liquid particles formed by the combustion of organic matter.
For example, cigarette smoke, oil smoke, smokes from burning of fossil fuel, garbage and dry leaves.

3. Dust composed of fine solid particles produced during crushing and grinding of solid materials.
For example, sand from sand blasting, saw dust from wood works, cement dust from cement factories and fly ash from power generating units.

Question 33.
Even though the use of pesticides increases crop production, they adversely affect the living organisms. Explain the function and the adverse effects of the pesticides.
Answer:
Pesticides are chemicals that are used to kill or stop the growth of unwanted organisms. But these pesticides can affect the health of human beings.
These are further classified as

Insecticides:
Insecticides like DDT, BHC, aldrin etc. can stay in soil for long period of time and are absorbed by soil. They contaminate root crops like carrot, raddish, etc.

Fungicide:
Organo mercury compounds are used as most common fungicide. They dissociate in soil to produce mercury which is highly toxic.

Herbicides:
Herbicides are the chemical compounds used to control unwanted plants. They are otherwise known as weed killers. Example sodium chlorate (NaClO₃) and sodium arsenite (Na₃AsO₃). Most of the herbicides are toxic to mammals.

Question 34.
Ethane burns completely in air to give CO₂, while in a limited supply of air gives CO. The same gases are found in automobile exhaust. Both CO and CO₂ are atmospheric pollutants.
Answer:
The major pollutants of oxides of carbon are carbon monoxide and carbon dioxide.

(i) Carbon Monoxide:
Carbon monoxide is a poisonous gas produced as a result of incomplete combustion of coal are firewood. It is released into the air mainly by. automobile exhaust. It binds with haemoglobin and form carboxy haemoglobin which impairs normal oxygen transport by blood and hence the oxygen carrying capacity of blood is reduced. This oxygen deficiency results in headache, dizziness, tension, Loss of consciousness, blurring of eye sight and cardiac arrest.

(ii) Carbon dioxide:
Carbon dioxide is released into the atmosphere mainly by the process of respiration, burning of fossil fuels, forest fire, decomposition of limestone in cement industry etc.

Green plants can convert CO₂ gas in the atmosphere into carbohydrate and oxygen through a process called photosynthesis. The increased CO₂ level in the atmosphere is responsible for global warming. It causes headache and nausea.

Question 35.
On the basis of chemical reactions involved, explain how do CFC’s cause depletion of ozone layer in stratosphere?
Answer:
In the presence of uv radiation, CFC’s break up into chlorine free radical
CF₂Cl₂ CF₂Cl + Cl
CFCl₃ CFCl₂ + Cl
Cl + O₃ → ClO + O₂
ClO + O → Cl + O₂

Chlorine radical is regenerated in the course of reaction. Due to this continuous attack of Cl thinning of Ozone layer takes place which leads to formation of the ozone hole.

It is estimated that for every reactive chlorine atom generated in the stratosphere 1,00,000 molecules of ozone are depleted.

Question 36.
How is acid rain formed? Explain its effect.
Answer:
Rain water normally has a pH of 5.6 due to dissolution of atmospheric CO₂ into it. Oxides, of sulphur and nitrogen in the atmosphere may be absorbed by droplets of water that make up clouds and get chemically converted into sulphuric acid and nitric acid respectively as a results of pH of rainwater drops to the level 5.6 hence it is called acid rain.

Acid rain is a by-product of a variety of sulphur and nitrogen oxides in the atmosphere. Burning of fossil fuels (coal and oil) in power stations, furnaces and petrol, diesel in motor engines produce sulphur dioxide and nitrogen oxides. The main contributors to acid rain are SO₂ and NO₂. They are converted into sulphuric acid and nitric acid respectively by the reaction with oxygen and water.

2SO₂ + O₂ + 2H₂O → 2H₂SO₄
4NO₂ + O₂ + 2H₂O → 4HNO₃

Question 37.
What is sewage? What are the major steps involved in the treatment of sewage waste?
Answer:
Objectives of waste water treatment:

1. To convert harmful compounds into harmless compounds.
2. To eliminate the offensive smell.
3. To remove the solid content of the sewage.
4. To destroy the disease-producing micro organisms.

Treatment process:
The sewage (or) wastewater treatment process involves the following steps.

I. Preliminary Treatment:
In this treatment, coarse solids and suspended impurities are removed by passing the wastewater through bar and mesh screens.

II. Primary treatment (or) Settling process:
In this treatment, greater proportion of the suspended inorganic and organic solids are removed from the liquid sewage by settling. In order to facilitate quick settling coagulants like alum, ferrous sulphate are added. These produce large gelatinous precipitates, which entrap finely divided organic matter and settle rapidly.
Al₂(SO₄)₃ + 6H₂O → 2Al(OH)₃ ↓ + 3H₂SO₄

III. Secondary (or) biological treatment:
In this treatment, biodegradable organic impurities are removed by aerobic bacteria. It removes upto 90 % of the oxygen demanding wastes. This is done by trickling filter or activated sludge process.

(a) Trickling filter process:
It is a circular tank and is filled with either coarse or crushed rock. Sewage is sprayed over this bed by means of slowly rotating arms.

When sewage starts percolating downwards, mocroorganisms present in the sewage grow on the surface of filtering media using organic material of the sewage as food. After completion of aerobic oxidation the treated sewage is taken to the settling tank and the sludge is removed. This process removes about 80 – 85 % of BOD.

(b) Activated sludge process:

Activated sludge is biologically active sewage and it has a large number of aerobic bacterias, which can easily oxidize the organic impurities.

The sewage effluent from primary treatment is mixed with the required amount of activated sludge. Then the mixture is aerated in the aeration tank. Under these condition, organic impurities of the sewage get oxidized rapidly by the microorganisms.

After aeration, the sewage is taken to the sedimentation tank. Sludges settle down in this tank, called activated sludge, a portion of which is used for seeding fresh batch of the sewage. This process removes about 90-95 % of BOD.

IV. Tertiary treatment:
After the secondary treatment, the sewage effluent has a lower BOD (25 ppm), which can be removed by the tertiary treatment process.

In the tertiary treatment, the effluent is introduced into a flocculation tank, where lime is added to remove phosphates. From the flocculation tank the effluent is led to ammonia stripping tower, where pH is maintained to 11 and the NH₄⁺ is converted to gaseous NH₃. Then the effluent is allowed to pass through activated charcoal column, where minute organic wastes are absorbed by charcoal. Finally the effluent water is treated with disinfectant (chlorine).

V. Disposal of sludge:
This is the last stage in the sewage treatment. Sludge formed from different steps can be disposed by

1. dumping into low – lying areas,
2. burning of sludge (incineration),
3. dumping into the sea,
4. using it as low grade fertilizers.

Question 38.
Differentiate the following:
(i) BOD and COD
(ii) Viable and non-viable particulate pollutants.
Answer:
(i) BOD and COD Biochemical oxygen demand (BOD):
The total amount of oxygen in milligrams consumed by microorganisms in decomposing the waste in one litre of water at 200°C for a period of 5 days is called biochemical oxygen demand (BOD) and its value is expressed in ppm. BOD is used as a measure of degree of water pollution. Clean water would have BOD value less than 5 ppm whereas highly polluted water has BOD value of 17 ppm or more.

Chemical Oxygen Demand (COD):
BOD measurement takes 5 days so another parameter called the Chemical Oxygen Demand (COD) is measured. Chemical oxygen demand (COD) is defined as the amount of oxygen required by the organic matter in a sample of water for its oxidation by a strong oxidising agent like K₂Cr₂O₇ in acid medium for a period of 2 hrs.

(ii) Viable and non – viable particulate pollutants:

Viable particulates:
The viable particulates are the small size living organisms such as bacteria, fungi, moulds, algae, etc. which are dispersed in air. Some of the fungi cause allergy in human beings and diseases in plants.

Non-viable particulates:
The non- viable particulates are small solid particles and liquid droplets suspended in air. They help in the transportation of viable particles. There are four types of non-viable particulates in the atmosphere.
Example:
Smoke, Dust, Mists, Fumes.

Question 39.
Explain how oxygen deficiency is cause by carbon monoxide in our blood? Give its effect.
Answer:
Carbon monoxide is a poisonous gas produced as a result of incomplete combustion of coal are firewood. It is released into the air mainly by automobile exhaust. It binds with haemoglobin and form carboxy haemoglobin which impairs normal oxygen transport by blood and hence the oxygen carrying capacity of blood is reduced.

This oxygen deficiency results in headache, dizziness, tension, Loss of consciousness, blurring of eye sight and cardiac arrest. Efforts to control environmental pollution have resulted in development of science for synthesis of chemical favorable to environment and it is called green chemistry.

Question 40.
What are the various methods you suggest to protect our environment from pollution?
Answer:

1. Waste management:
   Environmental pollution can be controlled by proper disposal of wastes.
2. Recycling:
   A large amount of disposed waste material can be reused by recycling the waste, thus it reduces the land fill and converts waste into useful forms.
3. Substitution of less toxic solvents for highly toxic ones used in certain industrial processes.
4. Use of fuels with lower sulphur content (e.g., washed coal)
5. Growing more trees.
6. Control measures in vehicle emissions are adequate.
7. Efforts to control environmental pollution have resulted in development of science for synthesis of chemical favourable to environment and it is called green chemistry.

11th Chemistry Guide Environmental Chemistry Additional Questions and Answers

I. Choose the best answer:

Question 1.
The type of pollution cause by spraying of DDT is
(a) air and soil
(b) air and water
(c) air
(d) air, water and soil
Answer:
(d) air, water and soil

Question 2.
The green house effect is caused by
(a) CO₂
(b) NO₂
(c) NO
(d) CO
Answer:
(a) CO₂

Question 3.
The gas responsible for ozone depletion:
(a) NO and freons
(b) SO₂
(c) CO₂
(d) CO
Answer:
(a) NO and freons

Question 4.
In Antartica ozone depletion is due to the formation of following compound
(a) acrolein
(b) peroxyacetyl nitrate
(c) SO₂ and NO₂
(d) chlorine nitrate
Answer:
(a) acrolein

Question 5.
The main element of smog is
(a) O₃ and PAN
(b) O₃
(c) PAN
(d) PPN and PBN
Answer:
(a) O₃ and PAN

Question 6.
Classical smog occurs in places of
(a) excess SO₂
(b) low temperature
(c) high temperature
(d) excess NH₃
Answer:
(b) low temperature

Question 7.
Which gas is responsible for ‘Bhopal Gas Tragedy’ in 1984?
(a) CO
(b) Methyl isocynate
(c) SO₂ and NO₂
(d) Ethyl isocynate
Answer:
(b) Methyl isocynate

Question 8.
Which gas is a main reason behind air pollution, is produced by
(a) sewage pollutant
(b) aerosols
(c) industrial remains
(d) Above all
Answer:
(b) aerosols

Question 9.
Which is a dangerous radiological pollutant?
(a) C¹⁴
(b) S³⁵
(c) Sr⁹⁰
(d) P³²
Answer:
(c) Sr⁹⁰

Question 10.
Which is related to ‘Green House Effect’?
(a) Farming of Green Plants
(b) Farming of Vegetables in Houses
(c) Global Warming
(d) Biodegradable pollutant
Answer:
(c) Global Warming

Question 11.
The uppermost region of the atmosphere is called
(a) Ionosphere
(b) Mesosphere
(c) Troposphere
(d) Stratosphere
Answer:
(d) Stratosphere

Question 12.
Which of the following is the coldest region of atmosphere
(a) Thermosphere
(b) Mesosphere
(c) Troposphere
(d) Stratosphere
Answer:
(b) Mesosphere

Question 13.
The region which is greatly affected by air pollution is
(a) Thermosphere
(b) Stratosphere
(c) Troposphere
(d) Mesosphere
Answer:
(c) Troposphere

Question 14.
The substance which is a primary pollutant?
(a) H₂SO₄
(b) CO
(c) PAN
(d) Aldehydes
Answer:
(b) CO

Question 15.
Depletion of ozone layer causes
(a) breast cancer
(b) blood cancer
(c) lung cancer
(d) skin cancer
Answer:
(d) skin cancer

Question 16.
Formation of London smog takes place in
(a) Winter during day time
(b) summer during day time
(c) summer during morning time
(d) winter during morning time
Answer:
(d) winter during morning time

Question 17.
The substance which is not regarded as a pollutant?
(a) NO₂
(b) CO₂
(c) O₃
(d) Hydrocarbons
Answer:
(b) CO₂

Question 18.
Green house gases
(a) allow shorter wavelength to enter earth’s atmosphere while doesn’t allow longer wavelength to leave the earth’s atmosphere.
(b) allow longer wavelength to enter earth atmosphere while doesn’t allow shorter wavelength to leave the surface.
(c) don’t have wavelength specific character.
(d) she wavelength specific behaviour near the earth while far from earth these have wavelength independent behavior.
Answer:
(a) allow shorter wavelength to enter earth’s atmosphere while doesn’t allow longer wavelength to leave the earth’s atmosphere.

Question 19.
Carbon monoxide (CO) is harmful to man because
(a) it forms carbolic acid
(b) it generates excess CO₂
(c) it is carcinogenic
(d) it competes with O₂ for haemoglobin
Answer:
(d) it competes with O₂ for haemoglobin

Question 20.
Today the concentration of green house gases is very high because of
(a) use of refrigerator
(b) increased combustion of oils and coal
(c) deforestation
(d) All of the above
Answer:
(d) All of the above

Question 21.
The quantity of CO₂ in atmosphere is
(a) 3.34 %
(b) 6.5 %
(c) 0.034 %
(d) 0.34 %
Answer:
(c) 0.034 %

Question 22.
BOD of pond is connected with
(a) microbes & organic matter
(b) organic matter
(c) microbes
(d) None of these
Answer:
(a) microbes & organic matter

Question 23.
When rain is accompanied by a thunderstorm, the collected rain water will have a pH value
(a) slightly lower than that of rain water without thunderstorm
(b) slightly higher than that when the thunderstorm is not there
(c) uninfluenced by occurrence of thunderstorm
(d) which depends upon the amount of dust in air
Answer:
(a) slightly lower than that of rain water without thunderstorm

Question 24.
Water pollution is caused by
(a) pesticides
(b) SO₂
(c) O₂
(d) CO₂
Answer:
(a) pesticides

Question 25.
Minamata disease of Japan is due to pollution of
(a) Aresenic
(b) Lead
(c) Cynide
(d) Mercury
Answer:
(d) Mercury

Question 26.
Which causes death of fish in water bodies polluted by sewage?
(a) Foul smell
(b) Pathogens
(c) Herbicides
(d) Decrease in D.O.
Answer:
(d) Decrease in D.O.

Question 27.
Sewage water is purified by
(a) aquatic plants
(b) microorganisms
(c) light
(d) fishes
Answer:
(b) microorganisms

Question 28.
Which pollutant is harmful for ‘Tajmahal’?
(a) Hydrogen
(b) O₂
(c) SO₂
(d) Chlorine
Answer:
(c) SO₂

Question 29.
Negative soil pollution is
(a) reduction in soil productivity due to erosion and over use
(b) reduction in soil productivity due to addition of pesticides and industrial wastes
(c) converting fertile land into barren land by dumping ash, sludge and garbage
(d) None of the above
Answer:
(a) reduction in soil productivity due to erosion and over use

Question 30.
The quantity of DDT in food chain
(a) decreases
(b) remains same
(c) increases
(d) changes
Answer:
(c) increases

Question 31.
Which is known as “Third poison of environment” and also creates ‘Blue baby syndrome’
(a) Nitrate present in water
(b) Phosphate and detergents found in water
(c) Cyanide
(d) Pesticides
Answer:
(b) Phosphate and detergents found in water

Question 32.
The substance having the largest concentration in acid rain?
(a) H₂CO₃
(b) HNO₃
(c) HCl
(d) H₂SO₄
Answer:
(d) H₂SO₄

Question 33.
Water is often treated with chlorine to
(a) remove hardness
(b) increase oxygen content
(c) kill germs
(d) remove suspended particles
Answer:
(c) kill germs

Question 34.
Thermal pollution affects mainly
(a) vegetation
(b) aquatic creature
(c) rocks
(d) air
Answer:
(b) aquatic creature

Question 35.
B.O.D test or biochemical oxygen demand test is made for measuring
(a) air pollution
(b) water pollution
(c) noise pollution
(d) soil pollution
Answer:
(b) water pollution

Question 36.
Brewery and sugar factory water alters the quality of a water body by increasing
(a) temperature
(b) turbidity
(C) pH
(d) COD and BOD
Answer:
(d) COD and BOD

Question 37.
A dental disease characterized by mottling of teeth is due to the presence of a certain chemical element in drinking water. Which is that element?
(a) Boron
(b) Chlorine
(c) Fluorine
(d) Mercury
Answer:
(c) Fluorine

Question 38.
The high amount of E.coli in water is an indicator of
(a) hardness of water
(b) industrial pollution
(c) sewage pollution
(d) presence of chlorine in the water
Answer:
(c) sewage pollution

Question 39.
A lake with an inflow of domestic sewage rich in organic waste may result in
(a) drying of the lake very soon due to algal bloom
(b) an increase production of fish due to a lot of nutrients
(c) death of fish due to lack of oxygen
(d) increased population of aquatic food web organisms
Answer:
(c) death of fish due to lack of oxygen

Question 40.
In which one of the following the BOD (Biochemical Oxygen Demand) of sewage(S), distillery effluent (DE), paper mill effluent (PE) and sugar mill effluent (SE) have been arranged in ascending order
(a) SE < S < PE < DE
(b) SE < PE < S < DE
(c) PE < S < SE < DE
(d) S < DE < PE < SE
Answer:
(c) PE < S < SE < DE

Question 41.
The greenhouse effect is because of the
(a) presence of gases, which in general are strong infrared absorbers, in the atmosphere
(b) presence of CO₂ only in the atmosphere
(c) presence of O₃ and CH₄ in the atmosphere
(d) N₂O and chlorofluoro hydrocarbons in the atmosphere
Answer:
(a) presence of gases, which in general are strong infrared absorbers, in the atmosphere

Question 42.
Which of the following is/are the hazardous pollutant(s) present in automobile exhaust gases?
(a) N₂
(b) CO
(c) CH₄
(d) Oxides of nitrogen
Answer:
(c) CH₄

Question 43.
Green chemistry means such reactions which:
(a) produce colour during reactions
(b) reduce the use and production of hazardous chemicals
(c) are related to the depletion of ozone layer
(d) study the reactions in plants
Answer:
(b) reduce the use and production of hazardous chemicals

Question 44.
Which one of the following statement is not true?
(a) pH of drinking water should be between 5.5 – 9.5.
(b) Concentration of DO below 6 ppm is good for the growth of fish.
(c) Clean water would have a BOD value of less than 5 ppm.
(d) Oxides of sulphur, nitrogen and carbon are the most widespread air pollutant.
Answer:
(b) Concentration of DO below 6 ppm is good for the growth of fish.

Question 45.
Which one of the following statements regarding photochemical smog is not correct?
(a) Carbon monoxide does not play any role in photochemical smog formation.
(b) photochemical smog is an oxidizing agent in character.
(c) photochemical smog is formed through photochemical reaction involving solar energy.
(d) Photochemical smog does not cause irritation in eyes and throat.
Answer:
(d) Photochemical smog does not cause irritation in eyes and throat.

Question 46.
Frequent occurrence of water blooms in a lake indicates
(a) nutrient deficiency
(b) oxygen deficiency
(c) excessive nutrient availability
(d) absence of herbivores in the lake
Answer:
(b) oxygen deficiency

Question 47.
The smog is essentially caused by the presence of
(a) Oxides of sulphur and nitrogen
(b) O₂ and N₂
(c) O₂ and O₃
(d) O₂ and N₂
Answer:
(a) Oxides of sulphur and nitrogen

Question 48.
Identify the wrong statement in the following.
(a) Chlorofluorocarbons are responsible for ozone layer depletion.
(b) Greenhouse effect is responsible for global warming.
(c) Ozone layer does not permit infrared radiation from the sun to reach the earth.
(d) Acid rain is mostly because of oxides of nitrogen and sulphur.
Answer:
(c) Ozone layer does not permit infrared radiation from the sun to reach the earth.

Question 49.
Identify the incorrect statement from the following.
(a) Ozone absorbs the intense ultraviolet radiation of the sun.
(b) Depletion of ozone layer is because of its chemical reactions with chlorofluoro alkanes.
(c) Ozone absorbs infrared radiation.
(d) Oxides of nitrogen in the atmosphere can cause the depletion of ozone layer.
Answer:
(c) Ozone absorbs infrared radiation

Question 50.
What is DDT among the following?
(a) Greenhouse gas
(b) A fertilizer
(c) Biodegradable pollutant
(d) Non – biodegradable pollutant
Answer:
(d) Non – biodegradable pollutant

Question 51.
The gas leaked from a storage tank of the Union Carbide plant in Bhopal gas tragedy was:
(a) Methyl isocyanate
(b) Methylamine
(c) Ammonia
(d) Phosgene
Answer:
(a) Methyl isocyanate

Question 52.
Black – foot disease is caused due to groundwater contaminated with excess of
(a) Nitrate
(b) Fluoride
(c) Arsenic
(d) Sulphur
Answer:
(c) Arsenic

Question 53.
Exposure of an organism to UV system causes
(a) photodynamic action
(b) formation of thymidine
(c) splitting of H – bonds of DNA
(d) splitting of phosphodiester bonds
Answer:
(c) splitting of H – bonds of DNA

Question 54.
Under column – I, a list of gases that are known to have a greenhouse effect is given. Relate them to their main source selecting from the given under Column – II:

Column – I	Column – II
A. Nitrous oxide	1. Secondary pollutant from car exhausts
B. Chlorofluoro carbon (CFCs)	2. Combustion of fossil fuels, wood, etc.
C. Methane	3. Denitrification
D. Ozone (O3)	4. refrigerators, aerosol, sprays
E. Carbondioxide	5. Cattle, rice fields, toilets

(a) A – 3, B – 4, C – 5, D – 1, E – 2
(b) A – 5, B – 1, C – 3, D – 4, E – 2
(c) A – 4, B – 5 , C – 1, D – 2, E – 3
(d) A – 1, B – 3, C – 4, D – 5, E – 2
Answer:
(a) A – 3, B – 4, C – 5, D – 1, E – 2

Question 55.
Minamata disease is a pollution related disease results form
(a) oil spills into sea
(b) accumulation of arsenic into atmosphere
(c) release of industrial waste mercury into bodies water
(d) release human organic waste into drinking water
Answer:
(c) release of industrial waste mercury into bodies water

Question 56.
Air pollution causing photochemical oxidants production include
(a) Carbon monoxide, sulphur dioxide
(b) Nitrous oxide, nitric acid fumes, nitric oxide
(c) Ozone, peroxyacetyl nitrate, aldehydes
(d) Oxygen, chlorine, fuming nitric acid
Answer:
(c) Ozone, peroxyacetyl nitrate, aldehydes

Question 57.
Photochemical smog formed in congested metropolitan cities mainly consists of
(a) ozone, peroxyacetyl nitrate and NO_x
(b) smoke, peroxyacetyl nitrate and SO₂
(c) hydrocarbons, SO₂ and CO₂
(d) hydrocarbons, ozone and SO_x
Answer:
(a) ozone, peroxyacetyl nitrate and NO_x

Question 58.
Which, one of the following statements is correct?
(a) Extensive use of chemical fertilizers may lead to eutrophication of nearby water bodies
(b) Both Azotobacter and Rhizobium fix atmospheric nitrogen in root nodules of plants
(c) Cyanobacteria such as Anabaena and Nostoc are important mobilizers of phosphates and potassium for plant nutrition in soil
(d) At present it is not possible to grow maize without chemical fertilizers
Answer:
(a) Extensive use of chemical fertilizers may lead to eutrophication of nearby water bodies

Question 59.
Reducing the use of non-biodegradable things will contribute of
(a) Increase in O₂
(b) Cyanophycean blooms occur
(c) Depletion of O₂ layers
(d) Eutrophication
Answer:
(a) Increase in O₂

Question 60.
Which of the following metal is a water pollutant and causes sterility in human. being?
(a) As
(b) Mn
(c) Mg
(d) Hg
Answer:
(b) Mn

Question 61.
Lichens do not like to grow in cities
(a) because of absence of the right type of algae and fungi
(b) because of lack of moisture
(c) because of SO₂ pollution
(d) because natural habitat is missing
Answer:
(c) because of SO₂ pollution

Question 62.
Limit of BOD prescribed by Central pollution Control Board for the discharge of industrial and municipal waste waters into natural surface waters, is
(a) < 100 ppm
(b) < 30 ppm
(c) < 3.0 ppm
(d) < 10 ppm
Answer:
(b) < 30 ppm

Question 63.
Which one of the following pairs is mismatched
(a) Fossil fuel burning – release of CO₂
(b) Nuclear power – radioactive wastes
(c) Solar energy – Greenhouse effect
(d) Biomass burning – release of CO₂
Answer:
(c) Solar energy – Greenhouse effect

Question 64.
In a coal fired power plant electrostatic precipitators are installed to control emission of
(a) SO₂
(b) NO_x
(c) SPM
(d) CO
Answer:
(c) SPM

Question 65.
The term “Bio – magnification” refers to the
(a) growth of organism due to food consumption
(b) increase in population size
(c) blowing up of environmental issues by man
(d) increase in the concentration of non – degradable pollutants as they pass through food chain
Answer:
(d) increase in the concentration of non – degradable pollutants as they pass through food chain

Question 66.
In almost all Indian metropolitan cities like Delhi, the major atmospheric pollutant(s) is / are
(a) suspended particulate matter (SPM)
(b) oxides of sulphur
(c) carbon dioxide and carbon monoxide
(d) oxides of nitrogen
Answer:
(a) suspended particulate matter (SPM)

Question 67.
In coming years, skin related disorders will be more common due to
(a) pollutants in air
(b) use of detergents
(c) water pollution
(d) depletion of ozone layer
Answer:
(d) depletion of ozone layer

Question 68.
Statement 1:
Inhabitants close to very busy airports are likely to experience health hazards.
Statement 2:
Sound level of jet aeroplanes usually exceeds 160 dB.
(a) Statement – 1 is True, Statement – 2 is True, Statement – 2 is a correct explanation for Statement – 1.
(b) Statement – 1 is True, Statement – 2 is True, Statement – 2 is not a correct explanation for statement – 1
(c) Statement – 1 is True, Statement – 2 is False
(d) Statement – 1 is False, Statement – 2 is True
Answer:
(a) Statement – 1 is True, Statement – 2 is True, Statement – 2 is a correct explanation for Statement – 1.

Question 69.
Statement 1:
Suspended particulate matter (SPM) is an important pollutant released by diesel vehicles.
Statement 2:
Catalytic converters greatly reduce pollution caused by automobiles.
(a) Statement – 1 is True, Statement – 2 is True, Statement -2 is a correct explanation for Statement – 1.
(b) Statement – 1 is True, Statement – 2 is True, Statement – 2 is not a correct explanation for statement – 1
(c) Statement – 1 is True, Statement – 2 is False
(d) Statement – 1 is False, Statement – 2 is True
Answer:
(b) Statement – 1 is True, Statement – 2 is True, Statement – 2 is not a correct explanation for statement – 1

Question 70.
Statement 1:
Eutrophication shows increase in productivity in water.
Statement 2:
With increasing eutrophication, the diversity of the phytoplankton increases.
(a) Statement – 1 is True, Statement – 2 is True, Statement -2 is a correct explanation for Statement – 1.
(b) Statement – 1 is True, Statement – 2 is True, Statement – 2 is not a correct explanation for statement – 1
(c) Statement – 1 is True, Statement – 2 is False
(d) Statement – 1 is False, Statement – 2 is True
Answer:
(b) Statement – 1 is True, Statement – 2 is True, Statement – 2 is not a correct explanation for statement – 1

Question 71.
Statement 1:
The main cause of the Bhopal gas tragedy was phosgene.
Statement 2:
Phosgene is a volatile liquid.
(a) Statement – 1 is True, Statement – 2 is True, Statement -2 is a correct explanation for Statement – 1.
(b) Statement – 1 is True, Statement – 2 is True, Statement – 2 is not a correct explanation for statement – 1
(c) Statement – 1 is True, Statement – 2 is False
(d) Statement – 1 is False, Statement – 2 is True
Answer:
(d) Statement – 1 is False, Statement – 2 is True

Question 72.
Statement 1:
CO₂ causes green house effect.
Statement 2:
Other gases do not show such effect.
(a) Statement – 1 is True, Statement – 2 is True, Statement -2 is a correct explanation for Statement – 1
(b) Statement – 1 is True, Statement – 2 is True, Statement – 2 is not a correct explanation for statement – 1
(c) Statement – 1 is True, Statement – 2 is False
(d) Statement – 1 is False, Statement – 2 is True
Answer:
(c) Statement – 1 is True, Statement – 2 is False

II. Very short question and answers (2 Marks):

Question 1.
What is called as environmental pollution?
Answer:
Any undesirable change in our environment that has harmful effects on plants, animals and human beings is called environmental pollution.

Question 2.
What are pollutants?
Answer:
The substances which cause pollution of environment are called pollutants.

Question 3.
Write the different types of atmospheric pollution.
Answer:

1. Air pollution
2. Water pollution
3. Soil pollution.

Question 4.
What is Air pollution?
Answer:
Any undesirable change in air which adversely affects living organisms is called air pollution. Air pollution is limited to troposphere and stratosphere. Air pollution is mainly due to the excessive discharge of undesirable foreign matter in to the atmospheric air.

Question 5.
What are the techniques adopt to reduce particulate pollutants?
Answer:
The particulates from air can be removed by using electrostatic precipitators, gravity settling chambers, and wet scrubbers or by cyclone collectors. These techniques are based on washing away or settling of the particulates.

Question 6.
Define soil pollution.
Answer:
Soil pollution is defined as the buildup of persistent toxic compounds, radioactive materials, chemical salts and disease causing agents in soils which have harmful effects on plant growth and animal health.

Question 7.
Write the effects that were caused by classical smog.
Answer:

1. Smog is primarily responsible for acid rain.
2. Smog results in poor visibility and it affects air and road transport.
3. It also causes bronchial irritation.

III. Short question and answers (3 Marks):

Question 1.
How the oxides of nitrogen pollute the atmospheric air?
Answer:
Oxides of nitrogen are produced during high temperature combustion processes, oxidation of nitrogen in air and from the combustion of fuels (coal, diesel, petrol etc.).
N₂ + O₂ 2NO
2NO + O₂ 2NO₂
NO + O₃ → NO₂ + O₂

The oxides of nitrogen are converted into nitric acid which comes, down in the form of acid rain. They also form reddish brown haze in heavy traffic. Nitrogen dioxide potentially damages plant leaves and retards photosynthesis. NO₂ is a respiratory irritant and it can cause asthma and lung injury. Nitrogen dioxide is also harmful to various textile fibres and metals.

Question 2.
How the hydrocarbon compounds make harmful effects on living things?
Answer:
The compounds composed of carbon and hydrogen only are called hydrocarbons. They are mainly produced naturally (marsh gas) and also by incomplete combustion of automobile fuel.

They are potential cancer causing (carcinogenic) agents. For example, polynuclear aromatic hydrocarbons (PAH) are carcinogenic, they cause irritation in eyes and mucous membranes.

Question 3.
Explain the environmental impact of ozone depletion.
Answer:
The formation and destruction of ozone is a regular natural process, which never disturbs the equilibrium level of ozone in the stratosphere. Any change in the equilibrium level of the ozone in the atmosphere will adversely affect life in the biosphere in the following ways.

Depletion of ozone layer will allow more UV rays to reach the earth surface and layer would cause skin cancer and also decrease the immunity level in human beings. UV radiation affects plant proteins which leads to harmful mutation of cells. UV radiation affects the growth of phytoplankton, as a result ocean food chain is disturbed and even damages the fish productivity.

Question 4.
Write the causes of water pollution.
Answer:
(i) Microbiological (Pathogens):
Disease causing microorganisms like bacteria, viruses and protozoa are most serious water pollutants. They come from domestic sewage and animal excreta. Fish and shellfish can become contaminated and people who eat them can become ill. Some serious diseases like polio and cholera are water borne diseases. Human excreta contain bacteria such as Escherichia coli and Streptococcus faecalis which cause gastrointestinal diseases.

(ii) Organic wastes:
Organic matter such as leaves, grass, trash etc can also pollute water. Water pollution is caused by excessive phytoplankton growth within water. Microorganisms present in water decompose these organic matter and consume dissolved oxygen in water.

Question 5.
Write a short note on Eutrophication.
Answer:
Eutrophication is a process by which water bodies receive excess nutrients that stimulates excessive plant growth (algae, other plant weeds). This enhanced plant growth in water bodies is called as algae bloom.

The growth of algae in extreme abundance covers the water surface and reduces the oxygen concentration in water. Thus, bloom-infested water inhibits the growth of other living organisms in the water body. This process in which the nutrient-rich water bodies support a dense plant population, kills animal life by depriving it of oxygen and results in loss of biodiversity is known as eutrophication.

Question 6.
Write the harmful effects those caused by chemical water pollutants.
Answer:

1. Cadmium and mercury can cause kidney damage.
2. Lead poisoning can leads to severe damage of kidneys, liver, brain etc. it also affects central nervous system
3. Polychlorinated biphenyls (PCBs) causes skin diseases and are carcinogenic in nature.

Question 7.
Distinguish between BOD and COD.
Answer:

BOD	COD
1. BOD is the amount of oxygen required for the biological decomposition of organic matter present in the water.	COD is the amount of oxygen required for chemical oxidation of organic matter using some oxidizing agent like K2Cr207 and KMn04.
2. It is an important indication of the amount of organic matter present in the river water.	It is carried out to determine the pollution strength of river water.
3. Since complete oxidation occurs in an indefinite period, the reaction period is taken as 5 days at 20°C.	It is a rapid process and takes only 8 hours.

IV. Long question and answer (5 Marks):

Question 1.
Explain the different layers of earth’s atmosphere.
Answer:
Troposphere:
The lowest layer of the atmosphere is called the troposphere and it extends from o – 10 km from the earth surface. About 80% of the mass of the atmosphere is in this layer. This troposphere in further divided as follows.

i) Hydrosphere:
Hydrosphere includes all types of water sources like oceans, seas, rivers, lakes, streams, underground water, polar icecaps, clouds etc. It covers about 75% of the earth’s surface. Hence the earth is called as a blue planet.

ii) Lithosphere:
Lithosphere includes soil, rocks and mountains which are solid components of earth.

iii) Biosphere:
It includes the lithosphere, hydrosphere and atmosphere integrating the living organism present in the lithosphere, hydrosphere and atmosphere.

Question 2.
How the oxides of sulphur pollute the atmospheric air?
Answer:
Sulphur dioxide and sulphur trioxide are produced by burning sulphur-containing fossil fuels arid roasting sulphide ores. Sulphur dioxide is a poisonous gas to both animals and plants. Sulphur dioxide causes eye irritation, coughing and respiratory asthma, bronchitis, etc.

Sulphur dioxide is oxidised into more harmful sulphur trioxide in the presence of particulate matter present in polluted air.
2SO₂ + O₂ 2SO₃

SO₃ combines with atmospheric water vapour to form H₂SO₄, which comes down in the form of acid rain.
SO₃ + H₂O → H₂SO₄

Question 3.
Explain the health effects of particulate pollutants for human health.
Answer:

1. Dust, mist, fumes,etc., are air borne particles which are dangerous for human health. Particulate pollutants bigger than 5 microns are likely to settle in the nasal passage whereas particles of about 10 micron enters the lungs easily and causes scaring or fibrosis of lung lining.
2. They irritate the lungs and causes cancer and a,sthma. This disease is also called pneumoconiosis. Coal miners may suffer from black lung disease. Textile workers may suffer from white lung disease.
3. Lead particulates affect children’s brain, interferes maturation of RBCs and even cause cancer.
4. Particulates in the atmosphere reduce visibility by scattering and absorption of sunlight. It is dangerous for aircraft and motor vehicles
5. Particulates provide nuclei for cloud formation and increase fog and rain.
6. Particulates deposit on plant leaves and hinder the intake of CO₂ from the air and affect photosynthesis.

Question 4.
Explain the effects of photo chemical smog and its control.
Answer:
The three main components of photo chemical smog are nitrogen oxide, ozone and oxidised hydro carbon like formaldehyde(HCHO), Acrolein (CH₂ = CH – CHO), peroxy acetyl nitrate (PAN). Photochemical smog causes irritation to eyes, skin and lungs, increase in chances of asthma.

High concentrations of ozone and NO can cause nose and throat irritation, chest pain, uncomfortable in breathing, etc. PAN is toxic to plants, attacks younger leaves and cause bronzing and glazing of their surfaces. It causes corrosion of metals stones, building materials and painted surfaces.

Control of Photo chemical smog:
The formation of photochemical smog can be suppressed by preventing the release of nitrogen oxides and hydrocarbons into the atmosphere from the motor vehicles by using catalytic convertors in engines. Plantation of certain trees like Pinus, Pyrus, Querus Vitus and juniparus can metabolise nitrogen oxide.

Question 5.
List out the major water pollutants and their sources.
Answer:

Pollutant	Sources
1.Microorganisms	Domestic sewage, domestic waste water, dung heap.
2. Organic wastes	Domestic sewage, animal excreta, food processing factory waste, detergents and decayed animals and plants.
3. Plant nutrients	Chemical fertilisers.
4. Heavy metals	Heavy metal producing factories.
5. Sediments	Soil erosion by agriculture and strip-mining.
6. Pesticides	Chemicals used for killing insects, fungi and weeds.
7. Radioactive	Mining of uranium containing minerals substances.
8. Heat	Water used for cooling in industries.

Question 6.
What are the major sources that cause soil pollution?
Answer:
Artificial fertilizers:
Soil nutrients are useful for growth of plants. Plants obtains carbon, hydrogen and oxygen from air or water, whereas other essential nutrients like nitrogen, phosphorous, potassium, calcium, magnesium, sulphur are being absorbed from soil. To remove the deficiency of nutrients in soil, farmers add artificial fertilizers. Increased use of phosphate fertilizers or excess use of artificial fertilizers like NPK in soil, results in reduced yield in that soil.

Pesticides:
Pesticides are the chemicals that are used to kill or stop the growth of unwanted organisms. But these pesticides can affect the health of human beings.
These are further classified as

Insecticides:
Insecticides like DDT, BHC, aldrin etc. can stay in soil for long period of time and are absorbed by soil. They contaminate root crops like carrot, raddish, etc.

Fungicide:
Organo mercury compounds Eire used as most common fungicide. They dissociate in soil to produce mercury which is highly toxic.

Herbicides:
Herbicides are the chemical compounds used to control unwanted plants. They are otherwise known as weed killers.
Example:
Simple sodium chlorate (NaClO₃) and sodium arsenite (Na₃AsO₃). Most of the herbicides are toxic to mammals.

Industrial wastes:
Industrial activities have been the biggest contributor to the soil pollution especially the mining Eind manufacturing activities.

Large number of toxic wastes are released from industries. Industrial wastes include cyanides, chromates, acids, alkalis, and metals like mercury, copper, zinc, cadmium and lead etc. These industrial wastes in the soil surface lie for a long time and make it unsuitable for use.

Question 7.
Explain the various contribution of green chemistry in our day to day life.
Answer:
(1) Dry cleaning of clothes:

Solvents like tetrachloroethylene used in dry cleaning of clothes, pollute the ground water and are carcinogenic. In the place of tetrachloroethylene, liquefied CO₂ with suitable detergent is an Alternate solvent used. Liquified CO₂ is not harmful to the ground water. Now a days H₂O₂ used for bleaching clothes in laundry, gives better results and utilizese less water.

(2) Bleaching of paper:

Conventional method of bleaching was done with chlorine. Now a days H₂O₂ can be used for bleaching paper in presence of catalyst.

(3) Synthesis of chemicals:

Acetaldehyde is now commercially prepared by one step oxidation of ethene in the presence of ionic catalyst in aqueous medium with 90% yield.

CH₂ = CH₂ + O CH₃CHO
Ethylene Acetaldehyde

(4) Instead of petrol, methanol is used as a fuel in automobiles:

Methanol is considered to be less expensive than other commercial fuel and gasoline. During the process of combustion, it provides a higher thermal efficiency and power output because of its high octane rating and high heat vapourization.

(5) Neem based pesticides have been synthesised, which are more safer than the chlorinated hydrocarbons:

Every individual has an important role for preventing pollution and improving our environment. We Eire responsible for environmental protection. Let us begin to save our environment and provide a clean earth for our future generations.

Tamilnadu State Board New Syllabus Samacheer Kalvi 11th Chemistry Guide Pdf Chapter 14 Haloalkanes and Haloarenes Text Book Back Questions and Answers, Notes.

Tamilnadu Samacheer Kalvi 11th Chemistry Solutions Chapter 14 Haloalkanes and Haloarenes

11th Chemistry Guide Haloalkanes and Haloarenes Text Book Back Questions and Answers

Textbook Evaluation:

I. Choose the best answer:

Question 1.
The IUPAC name of is
a) 2 – Bromo pent – 3 – ene
b) 4 – Bromo pent – 2 – ene
c) 2 – Bromo pent – 4 – ene
d) 4 – Bromo pent – 1 – ene
Answer:
b) 4 – Bromo pent – 2 – ene

Question 2.
Of the following compounds, which has the highest boiling point?
a) n – Butyl chloride
b) Isobutyl chloride
c) t – Butyl chloride
d) n – Propyl chloride
Answer:
a) n – Butyl chloride

Question 3.
Arrange the following compounds in increasing order of their density
A) CCl₄
B) CHCl₃
C) CH₂Cl₂
D) CH₃Cl
a) D < C < B < A
b) C > B > A > D
c) A < B < C < D
d) C > A > B > D
Answer:
a) D < C < B < A

Question 4.
With respect to the position of – Cl in the compound CH3 – CH = CH – CH₂ – Cl, it is classified as
a) Vinyl
b) Allyl
c) Secondary
d) Aralkyl
Answer:
b) Allyl

Question 5.
What should be the correct IUPAC name of diethyl chloromethane?
a) 3 – Chloro pentane
b) 1 – Chloropentane
c) 1 – Chloro – 1, 1 – diethyl methane
d) 1- Chloro-1-ethyl propane
Answer:
a) 3 – Chloro pentane

Question 6.
C – X bond is strongest in
a) Chloromethane
b) Iodomethane
c) Bromomethane
d) Fluoromethane
Answer:
d) Fluoromethane

Question 7.
In the reaction X is ______.

Answer:
b)

Question 8.
Which of the following compounds will give racemic mixture on nucleophilic substitution by OH^– ion?
i)

ii)

iii)
a) (i)
b) (ii) and (iii)
c) (iii)
d) (i) and (ii)
Answer:
c) (iii)

Question 9.
The treatment of ethyl formate with excess of RMgX gives
a)

b)
c) R – CHO
d) R – O – R
Answer:
c) R – CHO

Question 10.
Benzene reacts with Cl₂ in the presence of FeCl₃ and in absence of sunlight to form
a) Chlorobenzene
b) Benzyl chloride
c) Benzal chloride
d) Benzene hexachloride
Answer:
a) Chlorobenzene

Question 11.
The name of C₂F₄C₁₂ is
a) Freon – 112
b) Freon – 113
c) Freon – 114
d) Freon – 115
Answer:
c) Freon – 114

Question 12.
Which of the following reagent is helpful to differentiate ethylene dichloride and ehtylidene chloride?
a) Zn / methanol
b) KQH / ethanol
c) aqueous KOH
d) ZnCl₂ / Con HCl
Answer:
c) aqueous KOH

Question 13.
Match the compounds given in Column I with suitable items given in Column II:

Column I (Compound)	Column II (Uses)
A. Iodoform	1. Fire extinguisher
B. Carbon tetra chloride	2. Insecticide
C. CFC	3. Antiseptic
D. DDT	4. Refrigerants

Code
a) A → 2 B → 4 C → 1 D → 3
b) A → 3 B → 2 C → 4 D → 1
c) A → 1 B → 2 C → 3 D → 4
d) A → 3 B → 1 C → 4 D → 2
Answer:
d) A → 3 B → 1 C → 4 D → 2

Question 14.
Assertion:
Inmonohaloarenes, electrophilic substitution occurs at ortho and para positions.
Reason:
Halogen atom is a ring deactivator.
Assertion and Reason type questions.
Directions:
In the following questions, a statement of assertion (A) is followed by a statement of reason (R) mark the correct choice as
(i) If both assertion and reason are true and reason is the correct explanation of assertion.
(ii) If both assertion and reason are true but reason is not the correct explanation of assertion.
(iii) If assertion is true but reason is false.
(iv) If both assertion and reason are false.
a) (i)
b) (ii)
c) (iii)
d) (iv)
Answer:
b) (ii)

Question 15.
Consider the reaction,
CH₃CH₂CH₂Br + NaCN → CH₃CH₂CH₂CN + NaBr This reaction will be the fastest in
a) ethanol
b) methanol
c) DMF (N, N’ – dimethyl formamide)
d) water
Answer:
c) DMF (N, N’ – dimethyl formamide)

Question 16.
Freon – 12 manufactured from tetrachloro methane by
a) Wurtz reaction
b) Swarts reaction
c) Haloform reaction
d) Gattermann reaction
Answer:
b) Swarts reaction

Question 17.
The most easily hydrolysed molecules under S_N¹ condition is
a) allyl chloride
b) ethyl chloride
c) isopropyl chloride
d) benzyl chloride
Answer:
a) allyl chloride

Question 18.
The carbon cation formed in S_N¹ reaction of alkyl halide in the slow step is
a) sp³ hybridized
b) sp² hybridized
c) sp hybridized
d) none of these
Answer:
b) sp² hybridized

Question 19.
The major products obtained when chlorobenzene is nitrated with HNO₃ and con H₂SO₄
a) 1 – chloro – 4 – nitrobenzene
b) 1 – chloro – 2 – nitrobenzene
c) 1 – chloro – 3 – nitrobenzene
d) 1 – chloro – 1 – nitrobenzene
Answer:
a) 1 – chloro – 4 – nitrobenzene

Question 20.
Which one of the following is most reactive towards nucleophilic substitution reaction?
a)

b)

c)

d)
Answer:
d)

Question 21.
Ethylidene chloride on treatment with aqueous KOH gives
a) acetaldehyde
b) ethylene glycol
c) formaldehyde
d) glycoxal
Answer:
a) acetaldehyde

Question 22.
The raw material for Raschig process
a) chloro benzene
b) phenol
c) benzene
d) anisole
Answer:
c) benzene

Question 23.
Chloroform reacts with nitric acid to produce
a) nitro toluene
b) nitro glycerine
c) chloropicrin
d) chloropicric acid
Answer:
c) chloropicrin

Question 24.
Acetone X, X is
a) 2 – propanol
b) 2 – methyl – 2 – propanol
c) 1 – propanol
d) acetonol
Answer:
b) 2 – methyl – 2 – propanol

Question 25.
Silverpropionate when refluxed with Bromine in carbon tetrachloride gives
a) propionic acid
b) chloroethane
c) Bromo ethane
d) chloro propane
Answer:
c) bromo ethane

II. Write brief answer to the following questions:

Question 26.
Classify the following compounds in the form of alkyl, allylic, vinyl, benzylic halides.
i) CH₃ – CH = CH – Cl

ii) C₆H₅CH₂I

iii)

iv) CH₂ = CH – Cl
Answer:
i) CH₃ – CH = CH – Cl = Allylic halide

ii) C₆H₅CH₂I = Benzylic halide

iii) = Alkyl halide

iv) CH₂ = CH – Cl = Vinyl halide

Question 27.
Why chlorination of methane is not possible in dark?
Answer:
The reaction of chlorine and methane is a free radical reaction under the influence of light energy. Chlorine molecule first split into two Cl atoms or radicals. These are both very reactive species in contact with methane they form methyl radical and HCl.

Methyl radical further reacts with Cl to give CH₃Cl and another Cl atom thus of a chain reaction. So this reaction takes place only under the influence of light. Hence the reaction does not take place in dark condition.

Question 28.
How will you prepare n propyl iodide from n – propyl bromide?
Answer:
Finkelstein reaction,
nCH₃ – CH₂ – CH₂ – Br + NaI n – CH₃ – CH₂ – CH₂ – I + NaBr
n – propyl iodide                                              n- propyl bromide

Question 29.
Which alkyl halide from the following pair is
i) chiral
ii) undergoes faster S_N² reaction?

Answer:

It contains one chiral carbon atom.
2 – bromo butane undergoes S_N² mechanism faster than 1- Chloro butane.

Question 30.
How does chlorobenzene react with sodium in the presence of ether? What is the name of the reaction?
Answer:
Haloarenes react with sodium metal in dry ether, two aryl groups combine to give biaryl products.
This reaction is called fittig reaction.
C₆H₅Cl + 2Na + Cl – C₆H₅ C₆H₅ – C₆H₅ + 2NaCl
Chlorobenzene                                      Biphenyl

Question 31.
Give reasons for polarity of C – X bond in halo alkane.
Answer:
Carbon halogen bond is a polar bond as halogens are more electro negative than carbon. The carbon atom exhibits a partial positive charge (δ⁺) and halogen atom a partial negative charge (δ^–)

The C -X bond is formed by overlap of sp³ orbital of carbon atom with half-filled p- orbital of the halogen atom. The atomic size of halogen increases from fluorine to iodine, which increases the C – X bond length. Larger the size, greater is the bond length, and weaker is the bond formed. The bond strength of C – X decreases from C – F to C – I in CH₃X.

Question 32.
Why is it necessary to avoid even traces of moisture during the use of Grignard reagent?
Answer:
Grignard reagents are mostly reactive and react with the source of product to give hydrocarbons. Even alcohols, amines, H₂O are sufficiently acidic to convert them to corresponding hydrocarbons.
R Mg X + H₂O → RH +

Due to its high reactivity, it is necessary to avoid even traces of moisture from Grignard reagent.

Question 33.
What happens when acetyl chloride is treated with an excess of CH₃MgI?
Answer:

Question 34.
Arrange the following alkyl halide in increasing order of bond enthalpy of RX.
CH₃Br, CH₃F, CH₃Cl, CH₃I
Answer:
The order is:
CH₃I < CH₃Br < CH₃Cl < CH₃F.

Question 35.
What happens when chloroform reacts with oxygen in the presence of sunlight?
Answer:
2 CHCl₃ + O₂ → 2 COCl₂ + 2 HCl

Question 36.
Write down the possible isomers of C₅H₁₁Br and give their IUPAC and common names.
Answer:
C₅H₁₁Br – Possible isomers
1. CH₃ – CH₂ – CH₂ – CH₂ – CH₂ – Br → 1 – bromo pentane

2. → 2 – bromo pentane

3. → 3 – bromo pentane

4.  → 1 – bromo 2, 2 – dimethyl propane

5. → 1 – bromo 3 – methyl butane

6. → 2 – bromo 3 – methyl butane

7. → 2 – bromo 2 – methyl butane

8. → 1 – bromo 2- methyl butane

9. → (2S) – 1 – bromo 2 – methyl butane

10. → (2R) – 1 – bromo 2 – methyl butane

Question 37.
Mention any three methods of preparation of haloalkanes from alcohols.
Answer:
Haloalkanes are prepared by the following methods.
1) From alcohols:
Alcohols can be converted into halo alkenes by reacting it with any one of the following reagent.
1. Hydrogen halide
2. Phosphorous halides
3. Thionyl chloride.

a) Reaction with hydrogen halide:

Mixture of con. HCl and anhydrous ZnCl₂ is called Lucas Reagent.

The order of reactivity of halo acids with alcohol is in the order HI > HBr > HCl.
The order of reactivity of alcohols with halo acid is tertiary > secondary > primary.

b) Reaction with phosphorous halides:
Alcohols react with PX₅ or PX₃ to form haloalkanes.
Example:
CH₃CH₂OH + PCl₅ → CH₃CH₂Cl + POCl₃ + HCl
Ethane                      Chloro ethane

3CH₃CH₂OH + PCl₃ → 3 CH₃CH₂Cl + H₃PO₃
Ethanol                       Chloro ethane

c) Reaction with Thionyl chloride(Sulphonyl Chloride)
CH₃CH₃OH + SOCl₂ CH₃CH₂Cl + SO₂↑ + HCl↑
Ethanol                                      Chloro ethane

Question 38.
Compare S_N¹ and S_N² reaction mechanisms.
Answer:

	SN1	SN2
Rate law	Unimolecular (Substrate only)	Biomolecular (substrate and nucleophile)
“Big Barrier”	Carbocation stability	Steric hindrance
Alkyl halide (electrophile)	3° > 2° > 1°	1° > 2° > 3°
Nucleophile	Weak (generally neutral)	Strong (generally bearing a negative charge)
Solvent	Polar protic (e.g., alcohols)	Polar aprotic (e.g., DMSO, acetone)
Stereo Chemistry	Mix of retention and inversion	inversion

Question 39.
Reagents and the conditions used in the reactions are given below. Complete the table by writing down the product and the name of the reaction.

Answer:

Question 40.
Discuss the aromatic nucleophilic substitutions reaction of chlorobenzene.
Answer:
The halogen of haloarenes can be substituted by OH^–, NH₂^– or CN^– with appropriate nucleophilic reagents at high temperature and pressure.
Example:
(i) Chlorobenzene reacts with ammonium at 250 and at 50 atm to give aniline.
C₆H₅Cl + 2NH₃ C₆H₅NH₂ + NH₄Cl
Chlorobenzene                  Aniline

(ii) Chlorobenzcne reacts with CuCN in presence of pyridine at 250 to give phenyl cyanide.
C₆H₅Cl + CuCN C₆H₅CN + CuCl
Chlorobenzene                Phenyl cyanide

(iii) Dows process:
C₆H₅Cl + NaOH C₆H₅OH + NaCl
Chlorobenzene                   Phenol
This reaction is known as Dow’s process.

Question 41.
Account for the following:
(i) t – butyl chloride reacts with aqueous KOH by S_N¹ mechanism while n – butyl chloride reacts with S_N² mechanism.
(ii) p – dichloro benzene has higher melting point than those of o – and m – dichloro benzene.
Answer:
(i) t – butyl chloride reacts with aqueous KOH by S_N¹ mechanism while n – butyl chloride reacts with S_N² mechanism.
It general, S_N¹ reaction proceeds through the formation, of carbocation, The tert- butyl chloride readily loses Cl ion to form stable 3° carbocation. Therefore, it reacts with aqueous KOH by S_N¹ mechanism as:

On the other hand n-Butyl chloride does not undergo ionization to form n-Butyl carbocation (1°) because it is not stable. Therefore, it prefers to undergo reaction by S_N² mechanism, which occurs is one step through a transition state involving nucleophilic attack of OH^– ion from the backside with simultaneous expulsion of Cl^– ion from the front side.

S_N¹ mechanism follows the reactivity order as 3° > 2°> 1° while S_N² mechanism follows the reactivity order as 1° > 2° > 3°. Therefore, tert-butyl chloride (3°) reacts by S_N¹ mechanism while n-butyl chloride (1°) reacts by S_N² mechanism. (ii) p – dichloro benzene has higher melting point than those of o – and m – dicholoro benzene. The higher melting point of p – isomer is due to its symmetry which leads to more close packing of its molecules in the crystal lattice and consequently strong intermolecular attractive force which requires more energy for melting. p – Dihalo benzene > o – Dichloro benzene> m – Dichioro benzene
Melting point: 323 K 256 K 249 K

Question 42.
In an experiment methyl iodide in ether is allowed to stand over magnesium pieces. Magnesium dissolves and product is formed.
a) Name of the product and write the equation for the reaction.
b) Why all the reagents used in the reaction should be dry? Explain.
c) How is acetone prepared from the product obtained in the experiment?
Answer:
a) Name of the product and write the equation for the reaction.
CH₃I + Mg CH₃MgI

b) Why all the reagents used in the reaction should be dry? Explain.
All the reagents used in the reaction should be dry because reagent reacts with H20 to produce alkane. This is the reason that everything has to be very dry during the preparation of Grignard reagents.
CH₃ – MgI + H₂O → CH₄ +
Methane

c) How is acetone prepared from the product obtained in the experiment?

Question 43.
Write a chemical reaction useful to prepare the following.
i) Freon – 12 from Carbon tetrachloride
ii) Carbon tetrachloride from carbon disulphide.
Answer:
i) Freon – 12 from Carbon tetrachloride:
Freon – 12 is prepared by the action of hydrogen fluoride on carbon tetrachloride in the presence of catalytic amount of antimony pentachloride.
CCl₄ + 2HF 2HCl + CCl₂F₂
Carbon tetrachloride            Freon – 12

ii) Carbon tetrachloride from carbon disulphide.
Carbon disulphide reacts with chlorine gas in the presence of anhydrous AlCl3 as catalyst giving carbon tetra chloride.
CS₂ + 3 Cl₂ CCl₄ + S₂Cl₂
Carbon disulfide                Carbon tetrachloride

Question 44.
What are Freons? Discuss their uses and environmental effects.
Answer:
The chloro fluoro derivatives of methane and ethane are called freons.
Nomenclature:
Freon is represented as Freon – cba
Where a = number of carbon atoms – 1;
b = number of hydrogen atoms + 1
a = total number of fluorine atoms

Uses:
i) Freons are used as a refrigerants in refrigerators and air conditioners.
ii) It is used as a propellant for aerosols and foams
iii) It is used as propellant for foams to spray out deodorants, shaving creams, and insecticides.

Question 45.
Predict the products when bromo ethane is treated with the following.
i) KNO₂ ii) AgNO₂
Answer:
i) KNO₂:
Bromo ethane reacts with alcoholic solution of NaNO2 or KNO2 to form ethyl nitrite.
CH₃CH₂Br + KNO₂ → CH₃CH₂ – O – N = O + KBr
Bromoethane Ethyl nitrite

ii)AgNO₂:
Bromo ethane reacts with alcoholic solution of AgNO2 to form nitro ethane.
CH₃CH₂Br + AgNO₂ → CH₃CH₂ NO₂ + AgBr
Bromoethane                Nitro ethane

Question 46.
Explain the mechanism of S_N¹ reaction by highlighting the stereochemistry behind it.
Answer:

In S_N¹ reactions, if the alkyl halide is optically active, the product obtained in a racemic mixture. The intermolecular carbocation formed in slowest step being sp2 hybridised is planar species. Therefore the attack of the nucleophile OH on it, can occur from both the faces with equal case forming a mixture of two enantiomers. Thus S_N¹ reaction of optically active alkyl halides are accompained by racemisation.

Question 47.
Write short notes on the following.
i) Raschig process
ii) Dows process
iii) Darzen’s process
Answer:
i) Raschig process:
Chloro benzene is commercially prepared by passing a mixture of benzene vapour, air and HCl overheated cupric chloride, this reaction is called the Raschig process,

ii) Dows Process:
C₆H₅Cl + NaOH C₆H₅OH + NaCl
This reaction is known as Dows process.

iii) Darzen’s process:
CH₃CH₂OH + SOCl CH₃CH₂Cl + SO₂↑ + HCl↑
Ethanol Chloro ethane
This reaction is known as Darzen’s process.

Question 48.
Starting from CH₃MgI, How will you prepare the following?
i) Acetic acid
ii) Acetone
iii) Ethyl acetate
iv) Iso propyl alcohol
v) Methyl cyanide
Answer:
i) Acetic acid:
Solid carbon dioxide reacts with methyl magnesium iodide to form addition product which on hydrolysis yields aceti acid.

ii) Acetone:
Acetyl chloride reacts with methyl magnesium iodide and followed by acid hydrolysis to give acetone.

iii) Ethyl Acetate:
Ethyl chloroformate reacts with methyl magnesium iodide to form ethyl acetate.

iv) Isopropyl alcohol:
Aldehydes (Acetaldehyde) other than formaldehyde, react with methyl magnesium iodide to give addition product which on hydrolysis yields isopropyl alcohol.

v) Methyl cyanide:
Methyl magnesium iodide reacts with cyanogen chloride to give methyl cyanide.

Question 49.
Complete the following reactions.
i) CH₃ – CH = CH₂ + HBr
ii) CH₃ – CH₂ – Br + NaSH
iii) C₆H₅Cl + Mg
iv) CHCl₃ + HNO₃
v) CCl₄ + H₂O
Answer :
i) CH₃ – CH = CH₂ + HBr CH₃ – CH₂ – CH₂ – Br
Propene                                                   n – propyl bromide

ii) CH₃ – CH₂ – Br + NaSH CH₃ – CH₂ – SH + NaBr
Propyl bromide                                     Ethanethiol

iii) C₆H₅Cl (Chloro benzene) + Mg C₆H₅MgCl (Phenyl magnesium chloride)

iv) CHCl₃ + HNO₃ CCl₃NO₂ + H
Chloroform                               Chloropicrin

v) CCl₄ (Carbon tetrachloride) + H₂O COCl₂ (Carbonyl chloride) + 2HCl

Question 50.
Explain the preparation of the following compounds.
i) DDT
ii) Chloroform
iii) Biphrnyl
iv) Chloropicrin
v) Freon – 12
Answer:
i) DDT:
DDT can be prepared by heating a mixture of chlorobenzene with chloral (Trichloro acetaldehyde) in the presence of con.H₂SO₄.

ii) Chloroform:
Preparation:
Chloroform is prepared in the laboratory by the reaction between ethyl alcohol with bleaching powder followed by the distillation of the product chloroform. Bleaching powder act as a source of chlorine and calcium hydroxide. This reaction is called haloform reaction. The reaction proceeds in three steps as shown below.

Step – 1: Oxidation
CH₃CH₂OH + Cl₂ → CH₃CHO + 2HCl
Ethyl alcohol           Ethanal (Acetaldehyde)

Step – 2: Chlorination
CH₃CHO + 3Cl₂ → CCl₃CHO + 3HCl
Acetaldehyde        Trichloro acetaldehyde

Step – 3: Hydrolysis
2CCl₃CHO + Ca(OH)₂ → 2CHCl₃ + (HCOO)₂ Ca
Chloral                         chloroform

iii) Biphenyl:
Chloro benzene react with sodium metal in dry ether, to give biphenyl. This reaction is called fitting reaction.
C₆H₅Cl + 2 Na + Cl – C₆H₅ C₆H₅ – C₆H₅ + 2NaCl
Chloro benzene                                          Biphenyl

iv) Chloropicrin:
Chloroform reacts with nitric acid to form chloropicrin. (Trichloro nitro methane)
CHCl₃ + HNO₃ CCl₃NO₂ + H₂O
Chloroform                   Chloropicrin

v) Freon – 12
Freon – 12 is prepared by the action of hydrogen fluoride on carbon tetrachloride in the presence of catalytic amount of antimony pentachloride
CCl₄ + 2 HF 2 HCl + CCl₂F₂
Carbon tetrachloride                     Freon – 12

Question 51.
An organic compound (A) with molecular formula C₂H₅Cl reacts with KOH gives compounds (B) and with alcoholic KOH gives compound (C). Identify (A), (B), (C).
Answer:

Question 52.
Simplest alkene (A) reacts with HCl to form compound (B). Compound (B) reacts with ammonia to form compound (C) of molecular formula C₂H₇N. Compound (C) undergoes carbylamine test. Identify (A),
(B) and (C).
Answer:
CH₂ = CH₂ + HCl → C₂H₅Cl
(A) Ethylene              (B) Ethyl chloride

C₂H₅Cl + NH₃    →    C₂H₅NH₂ + HCl
(C) Ethyl chloride      (B) Ethyl amine

Question 53.
A hydrocarbon C₃H₆(A) reacts with HBr to form compound (B). Compound (B) reacts with aqueous potassium hydroxide to give (C) of molecular formula C₃H₆O. What are the (A), (B) and (C). Explain the reactions.
Answer:

Question 54.
Two isomers (A) and (B) have the same molecular formula C₂H₄Cl₂. Compound (A) reacts with aqueous KOH gives compound (C) of molecular formula C₂H₄O. Compound (B) reacts with aqueous KOH gives compound (D) of molecular formula C₂H₆O₂. Identify (A), (B), (C) and (D).
Answer:

11th Chemistry Guide Haloalkanes and Haloarenes Additional Questions and Answers

I. Choose the best answer:

Question 1.
Which of the following is 1° alkyl halide
a) R – CH₂ – X
b) R₂CHX
C) R₃C – X
d) R – H
Answer:
a) R – CH₂ – X

Question 2.
2° halide among the following
a) isopropyl chloride
b) iso – butyl chloride
c) n – propyl chloride
d) n – butyl chloride
Answer:
a) isopropyl chloride

Question 3.
Ethylidene dibromide is
a) CH₃CH₂Br
b) Br – CH₂ – CH₂ – Br
c) CH₃ – CHBr₂
d) CH₂ = CH Br
Answer:
c) CH₃ – CHBr₂

Question 4.
Which of the following is gemdihalide?
a) CH₃CHBrCH₂Br
b) CH₃CHBr₂
c) CH₃CHBrCH₂CH₂Br
d) BrCH₂CH₂Br
Answer:
b) CH₃CHBr₂

Question 5.
Vicinal dihalide is
a) CH₃CH₂Br
b) Br – CH₂ – CH₂ – Br
c) CH₃ – CHBr₂
d) CH₂ = CHBr
Answer:
b) Br – CH₂ – CH₂ – Br

Question 6.
The reagent used to get alkyl halide from alcohol
a) PCl₅
b) SOCl₂
c) Both a and b
d) Cl₂
Answer:
c) Both a and b

Question 7.
For the preparation of alkyl halides from alcohols which among the following cannot be used
a) PCl₅
b) SOCl₂
c) PCl₃
d) NaCl
Answer:
d) NaCl

Question 8.
In the preparation of alkyl halide from alkane and halogen which of the following reaction involved
a) Electrophilic addition
b) Nucleophilic addition
c) Electrophilic substitution
d) Nucleophilic substitution
Answer:
a) Electrophilic addition

Question 9.
In the preparation of alkyl halide from alkane and halogen which of the following reaction involved
a) Free radical substitution
b) Nucleophilic addition
c) Electrophilic substitution
d) Nucleophilic substitution
Answer:
a) Free radical substitution

Question 10.
Grignard reagent is formed when alkyl halide reacts with which one of the following
a) Mg in alcohol
b) Mg in acid
c) Mg in dry ether
d) MgO
Answer:
c) Mg in dry ether

Question 11.
When alkyl halide reacts with moist Ag₂O gives
a) alcohol
b) ether
c) alkane
d) Alkene
Answer:
a) alcohol

Question 12.
Alkyl halide on reduction with Zn + HCl gives
a) alcohol
b) alkene
c) alkane
d) ether
Answer:
c) alkane

Question 13.
Cyanide is formed as the major product of the reaction when alkyl halide is treated with one of the following :
a) AgNO₂
b) KNO₂
c) AgCN
d) KCN
Answer:
c) AgCN

Question 14.
Which of the reactions are most common in alkyl halides
a) Nucleophilic addition
b) Electrophilic addition
c) Nucleophilic substitution
d) Electrophilic substitution
Answer:
c) Nucleophilic substitution

Question 15.
Treatment of ammonia with excess of ethyl chloride will yield
a) Diethyl amine
b) Ethane
c) Tetra ethyl ammonium chloride
d) methyl amine
Answer:
c) Tetra ethyl ammonium chloride

Question 16.
In chloro ethane the carbon bearing halogen is bonded to ________.
a) three, primary
b) two, secondary
c) one, tertiary
d) two, primary
Answer:
d) two, primary

Question 17.
Which of the fallowing is used as refrigerant?
a) CH₃COCH₃
b) CCl₄
c) C₂H₅Cl
d) CF₄
Answer:
c) C₂H₅Cl

Question 18.
SN¹reaction occurs through the intermediate formation of
a) carbocation
b) carbanion
c) free radicals
d) transition
Answer:
a) carbocation

Question 19.
The rate of SN² reaction is maximum when the solvent is
a) Methyl alcohol
b) Water
c) Dimethyl sulphoxide
d) Benzene
Answer:
c) Dimethyl sulphoxide

Question 20.
The most reactive nucleophile among the following is
a) CH₃O^–
b) C₆H₅O^–
c) (CH₃)₂CHO^–
d) (CH₃)₃CO^–
Answer:
a) CH₃O^–

Question 21.
The correct order of reactivity towards nucleophilic substitution reaction is
a) CH₃F > CH₃Cl > CH₃Br > CH₃I
b) CH₃I > CH₃Br > CH₃Cl > CH₃F
C) CH₃I > CH₃Cl > CH₃Br > CH₃F
d) CH₃I > CH₃Br > CH₃F > CH₃Cl
Answer:
b) CH₃I > CH₃Br > CH₃Cl > CH₃F

Question 22.
In SN₂ reactions the order of reactivity of the halides.
CH₃X, C₂H₅X , n – C₃H₇X, n- C₄H₉X is
a) CH₃X > C₂H₅X > n – C₃H₇X > n – C₄H₉X
b) C₂H₅X > n – C₃H₇X > n – C₄H₉X > CH₃X
c) C₂H₅X > n – C₃H₇X > n – C₄H₉X < CH₃X
d) n – C₄H₉X > n – C₃H₇X > C₂H₅X > CH₃X
Answer:
a) CH₃X > C₂H₅X > n – C₃H₇X > n – C₄H₉X

Question 23.
SN² mechanism proceeds through the formation of a
a) carbocation
b) transition state
c) free radical
d) carbanion
Answer:
b) transition state

Question 24.
In Dow’s process the starting raw material is
a) Phenol
b) Chloro benzene
c) Aniline
d) Diazobenzene
Answer:
b) Chloro benzene

Question 25.
Chloro benzene is prepared commercially by
a) Dow’s process
b) Decon’s process
c) Raschig process
d) Etard’s process
Answer:
c) Raschig process

Question 26.
Chloro benzene is ________ reactive than benzene towards electrophilic substitution and directs incoming electrophile to the ______ position.
a) more, ortho & para
b) less, ortho & para
c) more, meta
d) less, meta
Answer:
b) less, ortho & para

Question 27.
The raw material for raschig; process is
a) chloro benzene
b) phenol
c) benzene
d) anisol
Answer:
c) benzene

Question 28.
Chloro benzene on treatment with sodium in dry ether gives diphenyl. The name of the reaction is
a) Fitting reaction
b) Wurtz fittig reaction
c) Wurtz reaction
d) Sandmeyer reaction
Answer:
a) Fitting reaction

Question 29.
An organic compound which produces a bluish green coloured flame on heating in the presence of copper is,
a) chloro benzene
b) benzaldehyde
c) aniline
d) benzoic acid
Answer:
a) chloro benzene

Question 30.
The raw materials for the commercial manufacture of DDT are
a) chloro benzene and chloroform
b) chloro benzene and chloro methane
c) chloro benzene and chloral
d) chloro benzene and iodoform
Answer:
c) chloro benzene and chloral

Question 31.
Iodoform is used as
a) anaesthetic
b) antiseptic
c) analgesic
d) anti febrin
Answer:
b) antiseptic

Question 32.
The following is used in paint removing
a) CHCl₃
b) CH₂Cl₂
c) CCl₄
d) CH₃CI
Answer:
b) CH₂Cl₂

Question 33.
In fire extinguishers, following is used
a) CHCl₃
b) CS₂
c) CCl₄
d) CH₂Cl₂
Answer:
c) CCl₄

Question 34.
The following is used for metal cleaning and finishing
a) CHCl₃
b) CHI₃
c) CH₂Cl₂
d) C₆H₆
Answer:
c) CH₂Cl₂

Question 35.
First chlorinated insecticide
a) DDT
b) Gammaxene
c) Iodoform
d) Freon
Answer:
a) DDT

Question 36.
The following is used as anaesthetic
a) C₂H₄
b) CHCl₃
c) CH₂Cl₂
d) DDT
Answer:
b) CHCl₃

Question 37.
Freon – 12 is
a) CF₃Cl
b) CHCl₂F
c) CF₂Cl₂
d) DDT
Answer:
c) CF₂Cl₂

Question 38.
The name of DDT
a) p, p’ – dichloro diphenyl trichloro ethane
b) p, p’ – dichloro diphenyl trichloro ethene
C) p, p’ – dichloro diphenyl tnchloro benzene
d) p, p’ – tetra chloro ethane
Answer:
a) p, p’ – dichloro diphenyl trichloro ethane

Question 39.
Freon R – 22 is
a) CHClF₂
b) CCl₂F₂
c) CH₃Cl
d) CH₂Cl₂
Answer:
a) CHClF₂

Question 40.
Molecular formula of DDT has
a) 5 Cl atoms
b) 4 Cl atoms
c) 3 Cl atoms
d) 2 Cl atoms
Answer:
a) 5 Cl atoms

Question 41.
What is DDT among the following
a) Green house gas
b) A fertilizer
c) Bio degradable pollutant
d) Non – Bio degradable pollutant
Answer:
d) Non – Bio degradable pollutant

Question 42.
The IUPAC name of (CH₃)₃CHCH₂Br is
a) 1 – bromo – 2 – methyl propane
b) 2 – bromo – 2 -methyl propane
c) 1 – bromo – 1 – methyl propane
d) 2 – bromo – 1 -methylpropane
Answer:
a) 1 – bromo – 2 – methyl propane

Question 43.
IUPAC name of allyl chloride is
a) 1 – chloro ethane
b) 3 – chloro- 1 – propyne
c) 3 – chloro – 1 – propene
d) 1 – chloro propane
Answer:
c) 3 – chloro – 1 – propene

Question 44.
The number of structural isomers possible with the formula C₄H₉Cl are
a) 5
b) 4
c) 3
d) 2
Answer:
b) 4

Question 45.
Density is highest for
a) CH₃Cl
b) CH₂Cl₂
c) CHCl₃
d) CCl₄
Answer:
d) CCl₄

Question 46.
C₂H₅OH X. In this reaction ‘X’ is
a) Ethanol
b) Ethylene chloride
c) ethylidene chloride
d) ethyl chloride
Answer:
d) ethyl chloride

Question 47.
Thionyl chloride is preferred in the preparation of chloro compound from alcohol since
a) Both the byproducts are gases and they escape out leaving product in pure state
b) It is a chlorinating agent
c) It is an oxidising agent
d) All other reagents are unstable
Answer:
a) Both the byproducts are gases and they escape out leaving product in pure state

Question 48.
The only alkene which gives primary alkyl halides on hydro halogenation
a) C₂H₄
b) C₃H₆
c) C₄H₈
d) C₅H₁₀
Answer:
a) C₂H₄

Question 49.
– OH cannot be replaced by – Cl if we use
a) PCl₅
b) PCl₃
c) S₂Cl₂
d) SOCl₂
Answer:
c) S₂Cl₂

Question 50.
In the hydrohalogenation of ethylene for adding HCl, the catalyst used is
a) Anhydrous AlCl₃
b) Conc. Sulphuric acid
c) Dilute Sulphuric acid
d) Anhydrous ZnCl₂
Answer:
a) Anhydrous AlCl₃

Question 51.
Which one of the following has the lowest boiling point?
a) CH₃Cl
b) C₂H₅Cl
c) C₂H₅Br
d) C₂H₅I
Answer:
a) CH₃Cl

Question 52.
Chloroethane is reacted with alcoholic potassium hydroxide. The product formed is
a) C₂H₆O
b) C₂H₆
c) C₂H₄
d) C₂H₄O
Answer:
c) C₂H₄

Question 53.
What is X in the following reaction? C₂H₅Cl + X → C₂H₅OH + KCl
a) KHCO3
b) alc. KOH
c) aq. KOH
d) K₂CO₃
Answer:
c) aq. KOH

Question 54.
Which of the following acids will give maximum yield of alkyl chloride in Hunsdiecker reaction
a) CH₃CH₂CH₂COOH
b) (CH₃)₂CHCOOH
c) (CH₃)₃CCOOH
d) C₆H₅CH (CH₃)COOH
Answer:
a) CH₃CH₂CH₂COOH

Question 55.
In the reaction sequence
C₂H₅Cl + KCN X. What is the molecular formula of X is
a) C₂H₅CN
b) C₂H₅NC
c) C₂H₅OH
d) C₂H₄O
Answer:
a) C₂H₅CN

Question 56.
Ethyl chloride on heating with silver cyanide forms a compound X. The functional isomer of X is
a) C₂H₅NC
b) C₂H₅NCN
c) H₃C – NH – CH₃
d) C₂H₅NH₂
Answer:
b) C₂H₅NCN

Question 57.
With Zn – Cu couple and C₂H₅OH, ethyl Iodide reacts to give
a) ethers
b) diethyl ether
c) Iodoform
d) Ethane
Answer:
d) Ethane

Question 58.
Ethyl bromide on boiling with alcoholic solutions of sodium hydroxide forms
a) Ethane
b) ethylene
c) ethyl alcohol
d) all of these
Answer:
b) ethylene

Question 59.
Following major compound is formed when ethyl chloride react with silver nitrite
a) Nitro ethane
b) Ethyl nitrite
c) Ethylene
d) Acetaldehyde
Answer:
b) Ethyl nitrite

Question 60.
Which of the following represents Williamson’s synthesis?
a) CH₃COOH + PCl₃ →
b) CH₃ – CH₂ – Cl + CH₃COOH →
c) CH₃ – CH₂ – ONa + CH₃ – CH₂ – Cl →
d) CH₃ – CH₂ – OH + Na →
Answer:
c) CH₃ – CH₂ – ONa + CH₃ – CH₂ – Cl →

Question 61.
The reaction of alkyl halide with benzene in presence of anhydrous A1Cl₃ gives alkyl benzene the reaction is known as
a) Friedel – craft’s reaction
b) Carbylamine reaction
c) Gattermann reaction
d) Wurtz reaction
Answer:
a) Friedel – craft’s reaction

Question 62.
A Grignard’s reagent reacts with water to give
a) ether
b) alkanes
c) amine
d) Alcohol
Answer:
b) alkanes

Question 63.
C₂H₅Cl + Mg → C₂H₅ MgCl in this reaction the solvent is
a) C₂H₅OH
b) Water
c) Dry ether
d) Acetone
Answer:
c) Dry ether

Question 64.
For a nucleophilic substitution reaction the rate was found in the order RI > RBr > RCl > RF then the reaction could be
a) S_N¹ only
b) S_N² only
c) Either S_N¹ or S_N²
d) Neither S_N¹ or S_N²
Answer:
c) Either S_N¹ or S_N²

Question 65.
S_N² reaction leads to
a) inversion of configuration
b) retention of configuration
c) partial racemisation
d) no racemisation
Answer:
a) inversion of configuration

Question 66.
Which of the following alkyl halide is hydrolysed by S_N¹ mechanism
a) CH₃Cl
b) CH₃ – CH₂ – Cl
c) CH₃ – CH₂ – CH₂ – Cl
d) (CH₃)₃CCl
Answer:
d) (CH₃)₃CCl

Question 67.
S_N¹ reaction is favoured by
a) non – polar solvents
b) Bulky group on the carbon atom attached to the halogen atom
c) Small groups on the carbon atom attached to halogen atom
d) All of the above
Answer:
b) Bulky group on the carbon atom attached to the halogen atom

Question 68.
Which of the following is not stereospecific
a) S_N¹
b) S_N²
c) E₂
d) Addition of Br₂ to ethylene in CCl₄
Answer:
a) S_N¹

Question 69.
Which of the following factors does not favour S_N¹ mechanism
a) Strong base
b) Polar solvent
c) Low. conc. of nucleophile
d) 3° halide
Answer:
c) Low. conc. of nucleophile

Question 70.
The order of reactivity of various alkyl halides toward SN1 reaction is
a) 3° > 2° > 1°
b) 1° > 2° > 3°
c) 3° = 2° = 1°
d) 1° > 3° > 2°
Answer:
a) 3° > 2° > 1°

Question 71.
In aryl halides carbon atom holding halogen is
a) sp² hybridised
b) sp hybridised
c) sp³ hybndised
d) sp³d hybridised
Answer:
a) sp² hybridised

Question 72.
Chloro benzene can be prepared by reacting benzene diazonlum chloride with
a) HCl
b) Cu₂Cl₂ / HCl
c) Cl₂ / AlCl₃
d) HNO₂
Answer:
b) Cu₂Cl₂ / HCl

Question 73.
+ Cl₂ X, X is
a) Chloro benzene
b) m – dichloro benzene
c) benzene hexachioride
d) p – dichlorobenzene
Answer:
a) Chloro benzene

Question 74.
The following is an example of Sandmeyer reaction
a) C₆H₅N₂⁺ Cl^– C₆H₅Cl
b) C₆H₅N₂⁺ Cl^– C₆H₅OH
c) C₆H₅N₂⁺ Cl^– C₆H₅F
d) C₆H₅N₂⁺ Cl^– C₆H₅Cl
Answer:
a) C₆H₅N₂⁺ Cl^– C₆H₅Cl

Question 75.
Chlorobenzene on reaction with CH₃Cl in presence of AlCl₃ gives
a) toulene
b) m – chloro toulene
c) only o – chloro toulene
d) mixture of o – and p – chlorotoulene
Answer:
d) mixture of o – and p – chlorotoulene

Question 76.
2C₆H₅Cl + 2Na → X, X is
a) toulene
b) biphenyl
C) phenyl ethane
d) 1 – chloro – 2 – phenyl ethane
Answer:
b) biphenyl

Question 77.
Chlorobenzene on fusing with solid NaOH gives
a) benzene
b) benzoic acid
c) phenol
d) benzene chloride
Answer:
c) phenol

Question 78.
Chlorobenzene on nitration gives major product of
a) 1 – chloro – 4 – nitro benzene
b) 1 – chloro – 3 – nitro benzene
c) 1, 4 – dinitro benzene
d) 2, 4, 6 – tri nitro benzene
Answer:
a) 1 – chloro – 4 – nitro benzene

Question 79.
The reaction C₆H₅I + 2 Na + CH₃I → C₆H₅CH₃ + 2 NaI is
a) Wurtz reaction
b) Fittig reaction
c) Wurtz-Fittig reaction
d) Sandmeyer reaction
Answer:
c) Wurtz-Fittig reaction

Question 80.
R – Cl + Nal R – I + NaCl. This reaction is
a) Wurtz reaction
b) Fittig reaction
c) Finkelstein reaction
d) Frankland reaction
Answer:
c) Finkelstein reaction

Question 81.
C₂H₅OH + SOCl₂ x + y + z. In this reaction x, y and z respectively are
a) C₂H₄Cl₂, SO₂, HCl
b) C₂H₅Cl, SO₂, HCl
c) C₂H₅Cl, SOCl, HCl
d) C₂H₄, SO₂, Cl₂
Answer:
b) C₂H₅Cl, SO₂, HCl’

Question 82.
C₂H₅Cl + AgOH → A + AgCl.
A + CH₃COCl → C + HCl. “C” is
a) Ethyl acetate
b) Methyl acetate
c) butanone – 2
d) propanone
Answer:
a) Ethyl acetate

Question 83.
The compound (B) in the below reaction is:
C₂H₅Cl A B
a) ethylene chloride
b) acetic acid
c) propionic acid
d) ethyl cyanide
Answer:
c) propionic acid

Question 84.
Chloro ethane reacts with X to form diethyl ether. What is X?
a) NaOH
b) H₂SO₄
c) C₂H₅ONa
d) Na₂S₂O₃
Answer:
c) C₂H₅ONa

Question 85.
1 – chlorobutane on reaction with alcoholic potash gives
a) 1 – butene
b) 1 – butanol
c) 1 – butyne
d) 2 – butanol
Answer:
a) 1 – butene

Question 86.
Propane nitrile may be prepared by heating
a) Propyl alcohol with KCN
b) ethyl chloride with KCN
c) Propyl chloride with KCN
d) ethyl chloride with KCN
Answer:
d) ethyl chloride with KCN

Question 87.
CH₃CH = CH₂ A B, B is
a) propanol – 2
b) propanal – 1
c) propanol – 1
d) propanal – 2
Answer:
c) propanol – 1

Question 88.
Y is

Answer:
c)

Question 89.
The correct order of increasing boiling points is
a) 1 – chloropropane < isopropylchloride < 1 – chlorobutane
b) isopropylchloride < 1 – chloropropane < 1 – chlorobutane
c) 1 – chlorobutane < isopropylchloride < 1 – chloropropane
d) 1 – chlorobutane < 1 – chloropropane < isopropylchloride
Answer:
b) isopropylchloride < 1 – chloropropane < 1 – chlorobutane

Question 90.
The correct order of decreasing S_N² reactivity
a) RCH₂X > R₂CHX > R₃CX
b) RCH₂X > R₃CX > R₂CHX
c) R₂CHX > R₃CX > RCH₂X
d) R₃CX > R₂CHX > RCH₂X
Answer:
a) RCH₂X > R₂CHX > R₃CX

II. Very short question and answer (2 Marks):

Question 1.
What are haloalkanes? Give example.
Answer:
Mono halogen derivatives of alkanes are called haloalkanes. Haloalkanes are represented by general formula R – X, Where, R is an alkyl group (C_nH_{2n + 1}) – and X is a halogen atom (X = F, Cl, Br or I). Haloalkanes are further classified into primary, secondary, tertiary haloalkane on the basis of type of carbon atom to which the halogen is attached.
Example:

Question 2.
How will you convert methane into tetra chloro methane?
Answer:
Chlorination of methane gives different products which have differences in the boiling points. Hence, these can be separated by fractional distillation.

Question 3.
What is Finkelstein reaction?
Answer:
Chloro or bromoalkane on heating with a concentrated solution of sodium iodide in dry acetone gives iodo alkanes. This reaction is called as Finkelstein reaction.
CH₃CH₂Br + NaI CH₃CH₂I + NaI
Bromo ethane Iodoethane

Question 4.
What is Swartz reaction?
Answer:
Chloro or bromo alkanes on heating with metallic fluorides like AgF or SbF₃ gives fluoro alkanes. This reaction is called Swarts reaction.
CH₃CH₂Br + AgF CH₃CH₂F + AgBr
Bromo ethane Fluoro ethane

Question 5.
What is Hunsdiecker reaction?
Answer:
Silver salts of fatty acids when refluxed with bromine in CCl₄ gives bromo alkane.
CH₃CH₂COOAg + Br₂ CH₃CH₂Br + CO₂ + AgBr
Silver propionate Bromo ethane

Question 6.
How is ehtyl magnesium bromide prepared from ethyl bromide?
Answer:
When a solution of ethyl bromide in ether is treated with magnesium, we get ethyl magnesium bromide.
CH₃ – CH₂ – Br + Mg CH₃CH₂MgBr
Ethyl bromide Ethyl magnesium bromide

Question 7.
How will you convert ethyl bromide into ethyl lithium?
Answer:
Ethyl bromide reacts with active metals like sodium, lead etc in the presence of dry ether to form ethyl lithium.
CH₃ CH₂ Br + 2Li CH₃ CH₂Li + LiBr
Ethyl bromide Ethyl Lithium

Question 8.
How is TEL prepared from ethyl bromide?
Answer:
When ethyl bromide reacts with Na / Pb alloy to give TEL.
4CH₃ CH₂ Br + 4Na/Pb → (CH₃CH₂)₄Pb + 4NaBr + 3Pb
Ethyl bromide Sodium-lead alloy Tetra ethyl lead (TEL)

Question 9.
What are organic metallic compounds? Give example.
Answer:
Organo metallic compounds are organic compounds in which there is a direct carbon-metal bond
Example:
CH₃ Mg I – Methyl magnesium iodide
CH₃CH₂Mg Br – Ethyl magnesium bromide

Question 10.
How is methane prepared from Grignard reagent?
Answer:
Compounds like water, alcohols and amines which contain active hydrogen atom react with Grignard reagents to form alkanes.
CH₃MgI + HO – H → CH₄ + Mg I (OH)

CH₃MgI + C₂H₅OH          CH₄ + MgI (OC₂H₅)
Ethyl alcohol                Methane

Question 11.
What are Haloarenes? Give a suitable example.
Answer:
Haloarenes are the compounds in which the halogen is directly attached to the benzene ring.
Example:

Question 12.
How is chloro benzene prepared from benzene by direct halogenation?
Answer:
Chloro benzene is prepared by the direct chlorination of benzene in the presence of lewis acid catalyst like FeCl₃.

Question 13.
Write a note on Sand Meyer reaction.
Answer:
When aqueous solution of benzene diazonium chloride is warmed with Cu₂Cl in HCl gives chioro benzene.

Question 14.
How is Iodo benzene prepared from benzene diazonium chloride?
Answer:
Iodo benzene is prepared by warming benzene diazonium chloride with an aqueous KI solution.
C₆H₅N₂Cl + Kl          C₆H₅I + N₂ + KCl
Benzene dizonium chloride        Iodo benzene

Question 15.
What happens when ethylidene dichloride is treated with Zinc dust in methanol?
Answer:
Gem dihalides and vic – dihalides on treatment with zinc dust in methanol give alkenes.
CH₃ – CHCl₂ + Zn CH₂ = CH₂ + ZnCl₂
Ethylidene dichloride                     Ethylene

Question 16.
How will you convert chloroform into methylene chloride?
Answer:
a) Reduction of chloroform in the presence of Zn + HCl gives methylene chloride.
CHCl₃ (chloroform) CH₂Cl (Methylene chloride) + HCl
b) Reduction of chloroform using H2/Ni
CHCl₃ (chloroform) CH₂Cl₂ (Methylene chloride) + HCl

Question 17.
Write the chlorination reaction of methane.
Answer:
Chlorination of methane gives methylene chloride
CH₄ CH₃Cl CH₂Cl₂
Methane                                               Methylene chloride

Question 18.
How is chloroform prepared from carbon tetrachloride?
Answer:
Carbon tetrachloride is reduced by iron powder in dilute HCl medium to form chloroform
CCl₄ (carbon tetrachloride) + 2[H] CHCl₃ (chloroform) + HCl

III. Short question and answers (3 Marks):

Question 1.
write IUPAC name of the following.
i)

ii)

iii)
Answer:
i)

ii)

iii)

Question 2.
Write the structure of the following compounds.
i) 1 – Bromo – 4 – ethyl cyclohexane
ii) 1, 4 – Dichlorobut – 2 – ene
iii) 2 – chloro – 3 – methyl pentane
Answer:
i) 1 -Bromo – 4 – ethyl cyclohexane:

ii) 1, 4 – Dichlorobut – 2 – ene
– Cl – CH₂ – CH = CH – CH₂ – Cl

iii) 2 – chloro – 3 – methyl pentane

Question 3.
Write any three methods of preparation of chloro ethane from ethanol.
Answer:
a) Reaction with hydrogen halide:
Ethanol is heated with HCl in presence of anhydrous ZnCl₂ to give ethyl chloride.
CH₃CH₂OH + HCl CH₃CH₂Cl + H₂O
Ethanol Chloroethane

b) Reaction with phosphorous halides:
Ethanol reacts with PCl₅ or PCl₃ it gives ethyl chloride.
CH₃CH₂OH + PCl₅ → CH₃CH₂Cl + POCl₃ + HCl
Ethanol                      Chloro ethane

3 CH₃CH₂OH + PCl₃ → 3CH₃CH₂Cl + H ₃PO₃
Ethanol                        Chloro ethane

C) Reaction with thionyl chloride (Sulphonyl chloride):
When ethanol reacts with SOCl₂ in presence of pyridine, it gives chloro ethane.
CH₃CH₂OH + SOCl₂ CH₃CH₂Cl + SO₂ + HCl
Ethanol                                            Chloro ethane

Question 4.
What happens when haloalkane reacts with aqueous alkali or most silver oxide?
Answer:
Ethyl bromide reacts with aqueous solution of KOH or moist silver oxide (Ag₂O/H₂O) to form ethanol.
CH₃ – CH₂ – Br + KOH (aq) CH₃CH₂ – OH + KBr
Bromoethane                                   Ethyl alcohol

CH₃ – CH₂ – Br   +   AgOH(aq)    CH₃CH₂ – OH + AgBr
Bromoethane         Moist silver oxide            Ethanol

Question 5.
Explain the ammonolysis reaction of bromo ethane.
Answer:
Ethyl bromide reacts with alcoholic ammonia solution to form ethylamine.
CH₃ – CH₂ – Br + H – NH₂ → CH₃ CH₂ – NH₂ + HBr
Bromo ethane                        Ethyl amine

However, with excess of ethyl bromide, secondary and tertiary amines along with quaternary ammonium salts are obtained.

Question 6.
What happens when bromoethane reacts with alcoholic KCN and alcoholic AgCN?
Answer:
Reaction with alcoholic KCN:
Ethyl bromide reacts with alcoholic KCN solution to form ethyl cyanides.
CH₃ – CH₂ – Br + KCN → CH₃ – CH₂ – CN + KBr
Bromoethane                    Ethyl cyanide

Reaction with alcoholic AgCN:
Haloalkanes react with alcoholic AgCN solution to form alkyl isocyanide.
CH₃CH₂Br + AgCN → CH₃CH₂NC + AgBr
Bromoethane           Ethyl isocyanide

Question 7.
How are the following compounds prepared from bromo ethane?
i) Ethane thiol
(ii) Diethyl ether
Answer:
i) Ethane thiol:
Ethyl bromide reacts with sodium or potassium hydrogen sulphide to form thio alcohols.
CH₃CH₂Br CH₃CH₂SH + NaBr
Bromo ethane                           Ethane thiol

ii) Diethyl ether:
Ethyl bromide, when boiled with sodium alkoxide gives diethyl ether. This method can be used to prepare mixed (unsymmetrical) ethers also.
CH₃ – CH₂Br +      NaOCH₂CH₃          CH₃CH₂ – O – CH₂CH₃ + NaBr
Bromo ethane        Sodium ethoxide                 diethyl ether

Question 8.
How is ethane prepared from the following compounds?
i) Bromo ethane ii) Iodo ethane
Answer:
i) From bromo ethane:
Ethyl bromide is reduced to ethane by treating with H₂ in the presence of metal catalyst like nickel, palladium etc or with hydroiodic acid in the presence of red phosphrous.
Ni(or)Pd
CH₃CH₂Br + H₂ CH₃ – CH₃ + HBr
Bromo ethane                              Ethane

ii) From iodo ethane:
Iodo ethane is reduced with H₂ in presence of Red P it gives ethane.
CH₃CH₂I + HI CH₃ – CH₃ + I₂
Iodo ethane                         Ethane

Question 9.
Write the uses of carbon tetra chloride.
Answer:

1. Carbon tetrachloride is used as dry cleaning agent.
2. It is used as a solvent for oils, fats and waxes
3. As the vapour of CCl₄ is non-combustible, it is used under the name pyrene for extinguishing the fire in oil or petrol.

Question 10.
Write the uses of Grignard reagents.
Answer:

1. Grignard reagents are synthetically very useful compounds. These reagents are converted to various organic compounds like alcohols, carboxylic acids, aldehydes and ketones.
2. The alkyl group being electron rich acts as a carbanion or a nucleophile.
3. They would attack polarized molecules at a point of low electron density. The following reactions illustrate the synthetic uses of Grignard reagent.

Question 11.
What is Balz – Schiemann reaction?
Answer:
Fluoro benzene is prepared by treating benzene diazonium chloride with fluoro boric acid. This reaction produces diazonium fluoroborate which on heating produces fluorobenzene. This reaction is called Balz – schiemann reaction.
C₆H₅N₂Cl + HBF₄ C₆H₅N₂ + BF₄^– C₆H₅ F + BF₃ + N₂
Benzene diazonium chloride                                          Fluorobenzene

Question 12.
Write the uses of chloro benzene.
Answer:

• Chloro benzene is used in the manufacture of pesticides like DDT
• It is used as high boiling solvent in organic synthesis.
• It is used as fibre – swelling agent in textile processing.

Question 13.
How is ethylidene dichloride prepared from
(i) Acetaldehyde
(ii) Acetylene
Answer:
i) Treating acetaldehyde with PCl₅:
CH₃CHO (Acetaldehyde) + PCl₅ → CH₃CHCl₂ (Ethylidene dichloride) + POCl

ii) Adding hydrogen chloride to acetylene

Question 14.
How is ethylene dichloride prepared from (i) Chloride (ii) PCl₅?
Answer:
i) Addition of chlorine to ethylene

ii) Action of PCl₅ (or HCl) on ethylene glycol

Question 15.
What happens when the following compounds are treated with alcoholic KOH?
i) Ethylidene dichloride
ii) Ethylene dichloride
Answer:
i) Ethylidene dichloride:

ii) Ethylene dichloride:

Question 16.
Write the uses of methylene chloride.
Answer:
Methylene chloride is used as

1. aerosol spray propellant
2. solvent in paint remover
3. process solvent in the manufacture of drugs
4. a metal cleaning solvent

Question 17.
How are the following compounds prepared from chlorobenzene?
i) Benzene
ii) Phenyl magnesium chloride
Answer:
i) C₆H₆ (Benzene):
Chlorbenzene undergoes reduction with Ni – Al alloy in the presence of NaOH gives benzene.
C₆H₅Cl + 2(H) C₆H₆ + HCl
Chloro benzene              Benzeneide

ii) Phenyl Magnesium chloride:
Chloro benzene reacts with magnesium to form phenyl magnesium chloride in tetra hydrofuran (THF).
C₆H₅Cl (Chloro benzene) + Mg C₆H₅MgCl (Phenyl magnesium chloride)

IV. Long question and answers (5 Marks):

Question 1.
Explain the S_N² mechanism of haloalkanes with suitable example.
Answer:
S2 stands for bimolecular nucleophilic substitution
“S” stands for substitution
“N” stands for nucleophilic
“2” stands for bimolecular (two molecules are involved in the rate determining step)
The rate of S_N² reaction depends upon the concentration of both alkyl halide and the nucleophile.
Rate of reaction = k₂ [alkyihalide] [nucleophile]
This S_N² reaction follows second order kinetics and occurs in one step.

This reaction involves the formation of a transition state in which both the reactant molecules are partially bonded to each other. The attack of nucleophile occurs from the back side and the halide ion leaves from the front side. The carbon at which substitution ocurs ha inverted configuration during the course of reaction just as an umbrella has tendency to invert in a wind storm. This inversion of configuration is called Walden inversion; after paul walden who first discovered the inversion of configuration of a compound in S_N² reaction.

We understand S_N² reaction mechanism by taking an example of reaction between chloromethane and aqueous KOH. S_N² reaction of an optically active haloalkane is always accompanied by inversion of configuration at the asymmetric centre.

 

Question 2.
Explain the S_N¹ mechanism of haloalkanes with suitable examples.
Answer:
S_N¹ stands for unimolecular nucleophilic substitution
‘S’ stands for substitution
‘N’ stands for nucleophilic
‘1’ stands for unimolecular (one molecule is involved in the rate determining step)
The rate of the following S_N¹ reaction depends upon the concentration of aikyl halide (RX) and is independent of the concentration of the nucleophile (OH-).
Rate of the reaction = k[alkyl halide]
R – Cl + OH^– → R – OH + Cl^–
This S_N¹ reaction follows first order kinetics and occurs in two steps.
We understand S_N¹ reaction mechanism by taking a reaction between tertiary hutyl bromide with aqueous KOH.

This reaction takes place in two steps aas shown below.

Step – 1:
Formation of carbocation:

t – butyl bromide

The polar C – Br bond breaks forming a carbocation and bromide ion. This step is slow and hence it is the rate determining step.

Step 2:
Nucleophilic attack on carbocation
The carbocation immediately reacts with the nucleophile. This step is fast and hence does not affect the rate of the reactions.

As shown above, the nucleophilic reagent OH~ can attack carbocation from both the sides, they will be mirror image of each other.

In the above example the substrate tert-butyl bromide is not optically active, hence the obtained product is optically inactive. If halo alkane substrate is optically active then, the product obtained will be optically inactive racemic mixture. As nucleophilic reagent OH- can attack carbocation from both the sides, to form equal proportion of dextro and levorotatory optically active isomers which form optically inactive racemic mixture.

Example :
Hydrolysis of optically active 2- bromo butane gives racemic mixture of ±butan-2-ol.

Question 3.
Explain the E₂ reaction mechanism with suitable example.
Answer:
E₂ stands for bimolecular elimination reaction
‘E’ stands for elimination
‘2’ stands for bimolecular
The rate of E₂ reaction depends on the concentration of alkyl halide and base

Rate = k₂ [alkyl halide] [base]
It is therefore, a second-order reaction generally primary alkyl halide undergoes this reaction in the presence of alcoholic KOH. E₂ is a one-step process in which the abstraction of the proton from the p carbon and expulsion of halide from the carbon occurs simultaneously. The mechanism is shown below.

Question 4.
Explain the E₁ reaction mechanism with suitable example.
Answer:
E₁ stands for unimolecular elimination reaction
‘E’ stands for elimination ‘1’ stands for unimolecular
The rate of E₁ reaction depends on the concentration of alkyl halide only and hence
rate = k [alkyl halide]
Generally, tertiary alkyl halide which undergoes elimination reaction by this mechanism in the presence of alcoholic KOH following first order kinetics is a two step process. The mechanism is shown by taking following example.

step – 1:
Heterolytic fission to yield a carbocation:

Step – 2:
Elimination of a proton from the β – carbon to produce an alkene:

Question 5.
How are the following compounds prepared from Methyl magnesium iodide?
(i) Ethanol
(ii) Tert-butyl alcohol
(iii) Acetaldehyde
Answer:
(i) Ethanol:
Formaldehyde reacts with methyl magnesium iodide to give addition products which on hydrolysis yield ethanol.

(ii) Tert-butyl alcohol:
Acetone reacts with methyl magnesium iodide to give an additional product which on hydrolysis yields tert butyl alcohol.

(iii) Acetaldehyde:
Ethyl formate reacts with methyl magnesium iodide and followed by acid hydrolysis, it forms Acetaldehyde.

Question 6.
How is ethylene dichloride converted into
i) Acetaldehyde
ii) Ethylene glycol
ii) Ethylene
Answer:
i) Acetaldehyde:
(Hydrolysis with aqueous NaOH or KOH)
Ethylidene chloride reacts with aqueous KOH to give acetaldehyde.

ii) Ethylene glycol :
Ethylene chloride reacts with aqueous KOH, it gives glycol.

iii) Ethylene:
Ethylene dichloride is heated with Zinc in presence of methanol gives ehtylene.

Question 7.
How are the following compounds prepared from chloroform?
(i) Phosgene
(ii) Methylene chloride
(iii) Methyl isocyanide
Answer:
(i) Phosgene:
Chloroform undergoes oxidation in the presence of light and air to form phosgene (carbonyl chloride)

Since phosgene is very poisonous, its presence makes chloroform unfit for use as an anaesthetic.

(ii) Methylene chloride:
Chloroform undergoes reduction with zinc and HCl in the presence of ethyl alcohol to form methylene chloride.
CHCl₃ (Chloroform) + 2(H) CH₂Cl₂ (Methylene chloride)+ Cl₂

(iii) Methyl isocyanide:
Chloroform reacts with aliphatic or aromatic primary amine and alcoholic caustic potash, to give foul-smelling alkyl isocyanide (carbylamines).
CH₃NH2     +     CHCl₂ + 3KOH → CH₃NC + 3KCl + 3H₂O
Methylamine Chloroform          Methyl isocyanide

Question 8.
Discuss the aromatic electrophilic substitutions reaction of chlorobenzene.
Answer:

Tamilnadu State Board New Syllabus Samacheer Kalvi 11th Bio Zoology Guide Pdf Chapter 12 Trends in Economic Zoology Text Book Back Questions and Answers, Notes.

Tamilnadu Samacheer Kalvi 11th Bio Zoology Guide Chapter Chapter 12 Trends in Economic Zoology

11th Bio Zoology Guide Trends in Economic Zoology Text Book Back Questions and Answers

Part I

Question 1.
Which one of the following is not related to vermiculture?
a) Maintains soil fertility
b) Break down of inorganic matter
c) Gives porosity, aeration and moister holding capacity
d) Degradation of non biodegradable solid waste

a) a and b is correct
b) c and d is correct
c) b and d is not correct
d) a and c is not correct
Answer:
c) b and d is not correct

Question 2.
Which one of the following is not an endemic species of earthworm?
a) Perionyx
b) Lampito
c) Eudrillus
d) Octochaetona
Answer:
c) Eudrillus

Question 3.
Match the following
1) Bombyxmori-
a) Champa – I) Muga
2) Antheraeaassamensis
b) Mulberry – II) Eri
3) Antheraeamylitta-
c) Arjun – III) Tassar
4) Attacus ricini –
d) Castor – IV) Mulberry

Select the correct one
a) 1-b-IV
b) 2-a-I
c) 3-c -III
d) 4-d-II
Answer:
c) 3-c -III

Question 4.
Silk is obtained from
a) Laccifer lacca
b) Nosema bombycis
c) Attacus ricird
d) Attacus mylitta
Answer:
c) Attacus ricird

Question 5.
Assertion: Nuptial flight is a unique flight taken by the queen bee followed by serveral drones.
Reason: The queen bee produces a chemical substance called pheromone. The drones in that area are attracted to the pheromone and then mating takes place.
a) Assertion and reason is correct but not related
b) Assertion and reason is incorrect but related
c) Assertion and reason is correct but related
d) Assertion and reason is incorrect but not related
Answer:
c) Assertion and reason is correct but related

Question 6.
Rearing of honey bee is called
a) Sericulture
b) Lac culture
c) Vermiculture
d) Apiculture
Answer:
d) Apiculture

Question 7.
Which of the statement regarding Lac insect
a) A microscopic, resinous crawling scale insect
b) Inserts its proboscis into plant tissue suck juices and grows
c) Secretes lac from the hind end of body.
d) The male lac insect is responsible for large scale production of lac.
Answer:
d) The male lac insect is responsible for large scale production of lac.

Question 8.
Aquaponics is a technique which is
a) A combination of aquaculture and fish culture
b) A combination of aquaculture and hydroponics
c) A combination of vermiculture and hydroponics
d) A combination of aquaculture and prawn culture
Answer:
b) A combination of aquaculture and hydroponics

Question 9.
Prawn belongs to the class
a) Crustacea
b) Annelida
c) Coelenterata
d) Echinodermata
Answer:
a) Crustacea

Question 10.
Pearl oyster belongs to the class
a) Gastropoda
b) Cephalopoda
c) Scaphapoda
d) Pelecypoda
Answer:
d) Pelecypoda

Question 11.
Inland fisheries are
a) deep sea fishing
b) capturing fishes from sea coast
c) Raising and capturing fishes in fresh water
d) oil extraction from fish
Answer:
c) Raising and capturing fishes in fresh water

Question 12.
Induced breeding technique is used in
a) Marine fishery
b) Capture fishery
c) Culture fishery
d) Inland fishery
Answer:
d) Inland fishery

Question 13.
Isinglass is used in
a) Preparation
b) Clearing of wines
c) Distillation of wines
d) Preservation of wines
Answer:
b) Clearing of wines

Question 14.
Animal husbandry is the science of rearing, feeding and caring, breeding and disease control of animals. It ensures supply of proper nutrition to our growing population through activities like increased production and improvement of animal products like milk, eggs, meat, honey etc.
a) Poultry production depends upon the photoperiod. Discuss
b) Polyculture of fishes is of great importance.
Answer:
a) Poultry production depends upon the photoperiod:

• The photoperiod stimulates the growth and breeding of birds.
• It increases the life span of birds
• As it increases the metabolic rate the egg-laying fowl’s wifi lay more eggs.
• The light induces the endocrine glands and increases hormone secretion.
• The light intensity depends on its wavelengths.

b) Polyculture of fishes is of great importance:

• In polyculture, fishes will not fight for food.
• No deficiency of oxygen.
• In this culture the upper layer fishes feeds on phy to and zooplanktons the middle layer fishes feeds on
• submerged plants and fishes lives in the deeper layers feeds on bottom dwellers debris of plants and animals.
• In polyculture the fishes use the maximum food to convert it into meat.
• Fishes have high growth rate in short periods.
  Eg.: Catlacatla, cirrhinus mrigla labeorohita are cultured through polyculture.

Question 15.
Assertion: The best quality of pearl is known as lingha pearl and obtained from marine oysters.
Reason: Nacre is secreted continuously by the epithelial layer of the mantle and deposited around the foreign particle
a) Assertion is true Reason is false
b) Assertion and Reason is false
c) Asserion is false but Reason is true
d) Assertion and Reason are true
Answer:
d) Assertion and Reason are true

Question 16.
Choose the correctly matched pair
a) Egg layers-Brahma
c) Dual purpose-White plymouth rock
b) Broiler types -Leghorn
d) Ornamental breeds -Silkie
Answer:
d) Ornamental breeds -Silkie

Question 17.
Write the advantages of vermicomposting.
Answer:

1. Vermicomposting provides excellent organic manure for sustainable agro-practices.
2. Marketing of vermicompost can provide a supplementary income.
3. Vermicompost is rich in essential plant nutrients.
4. It improves soil structure, texture, aeration, and water holding capacity and prevents soil erosion.
5. It is rich in nutrients and an eco-friendly amendment to soil for farming and terrace gardening,
6. It enhances seed germination and ensures good plant growth.

Question 18.
Name the three castes in a honey bee colony.
Answer:

1. Queen bee
2. Drone
3. Worker bee

Question 19.
Name the following

1. The largest bee in the colony:
2. The kind of flight which the new virgin queen takes along with the drones out of the hive:

Answer:

1. The largest bee in the colony – The queen bee
2. The kind of flight which the new virgin queen takes along with the drones out of the hive – Nuptial flight.

Question 20.
What are the main duties of a worker bee?
Answer:
Each worker has to perform different types of work in her lifetime. During the first half of her life, she becomes a nurse bee attending to indoor duties such as secretion of royal jelly, prepares bee- bread to feed the larvae, feeds the queen, takes care of the queen and drones, secretes beeswax, builds combs, cleans and fans the beehive. Then she becomes a soldier and guards the beehive. In the second half of her life lasting for three weeks, she searches and gathers the pollen, nectar, propolis, and water.

Question 21.
What happens to the drones after the mating flight?
Answer:
The drones are attracted to the pheromones of the queen bee and mating taking place The drone dies after copulation

Question 22.
Give the economic importance of silkworm?
Answer:

1. Rearing of silkworm on a commercial scale is called sericulture.
2. It is an agro-based industry comprising of
   • Cultivation of food plants for the silkworms.
   • Rearing of silkworms.
   • Reeling and spinning of silk.
3. Silk fibres are utilized in preparing silk clothes.
4. Silk is used in industries and for military purposes.
5. Silk is used in the manufacture of fishing fibres, parachutes, cartridge bags, insulation coils for telephone, wireless receivers, tyres of racing cars, filter fibres, in medical dressings and suture materials.

Question 23.
What are the nutritive values of fishes?
Answer:

• Fishes form a rich source of protein food.
• It is a good stable food to tide over the nutritional needs of man.
• Fish species such as sardines mackeral, tuna herrings have high amino acid concentrations.
• They have histidine which is responsible for the meaty flavor of the flesh.
• It is rich in omega 3 fatty acids.
• Minerals such as calcium magnesium phosphorus potassium iron-manganese iodine and copper is present in fishes.

Question 24.
Give the economic importance of prawn fishery?
Answer:
The flesh of prawns is palatable and rich in glycogen, a protein with low-fat content.

Question 25.
Give the economic importance of lac insect.
Answer:

• Lac is used as a sealing wax and adhesive for optical instruments.
• It is a good insulator.
• It is used in the preparations of shoe and leather polishes and as a protective coating of wood.
• It is used in laminating paper board photographs, plastic moulded articles.
• Used as a filling material for gold ornaments.

Question 26.
List any three common uses of shellac.
Answer:

1. Shellac with denatured alcohol is used to remove dust on the walls.
2. Coating of metals with shellac prevents rusting.
3. Shellac coating on citrus fruits increases their shelf life.

Question 27.
Name any two trees on which lac insect grows?
Answer:

1. Acacia catechu
2. Acacia nilotica

Question 28.
What is seed lac?
Answer:
The lac after grinding the dust particles are removed. The resultant lac is called ‘seed lac’.

Question 29.
Define cross-breeding?
Answer:
Breeding between a superior male of one breed with a superior female of another breed is known as cross-breeding.

Question 30.
What are the advantages of artificial insemination?
Answer:

• It increases the rate of conception.
• It avoids genital diseases.
• Semen can be collected from injured bulls which have desirable traits.
• Superior animals located apart can be bred successfully.

Question 31.
Discuss the various techniques adopted in cattle breeding?
Answer:
There are two methods of animal breeding, namely inbreeding and outbreeding.
1. Inbreeding:
Breeding between animals of the same breed for 4-6 generations is called inbreeding.

2. Outbreeding:
The breeding between unrelated animals is called outbreeding. It is done in three ways;

• Outcrossing: It is the breeding between unrelated animals of the same breed but having no common ancestry. The offspring of such a cross is called an outcross.
• Crossbreeding: Breeding between a superior male of one breed with a superior female of another breed. The cross-bred progeny has superior traits (hybrid vigour or heterosis).
• Interspecific hybridization: In this method of breeding mating is between male and females of two different species.

Question 32.
Mention the advantages of MOET.
Answer:
The advantage of this technology is to produce high milk-yielding females and high-quality meat-yielding bulls in a short time.

Question 33.
Write the peculiar characters of the duck.
Answer:
The peculiarity of ducks:
The ducks body is fully covered with oily feathers. They have a layer of fat under their skin which prevents it from getting wet. They lay eggs at night or in the morning. The ducks feed on rice bran, kitchen wastes, waste fish, and snails.

Part – II

11th Bio Zoology Guide Trends in Economic Zoology Additional Important Questions and Answers

I. Choose The Best Options

Question 1.
What is the primary use of earthworm?
a) Vermicompost
b) Increase the agriculture
c) To increase the fish culture
d) All the above
Answer:
a) Vermicompost

Question 2.
Who has proposed the term vermi tech?
a) Sultan Ismail
b) Darwin
c) Linnaeus
d) Albert William
Answer:
a) Sultan Ismail

Question 3.
……………………. are the biological indicators of soil fertility?
a) Vermicast
b) Earthworm
c) Vermi excreta
d) Vermicompost
Answer:
b) Earthworm

Question 4.
Which of the following is the earthworm of the native soil?
a) Periyonx Eisenia
b) Eudrilus eugeniae lampito mauritii
c) Periyonyx excavatus, octohaetona
d) all the above
Answer:
c) Periyonyx excavates, octohaetona

Question 5.
Which is called commercial fibre?
a) Silk fibre
b) Nylon fibre
c) Cofton fibre
d) Jute fibre
Answer:
a) Silk fibre

Question 6.
Who has known the utility of silk even before 3000 years?
a) Europe
b) African’s
c) China
d) India
Answer:
c) China

Question 7.
…………………… More than countries in the world are practicing sericulture?
a) 29
b) 40
c) 10
d) 15
Answer:
a) 29

Question 8.
Match and find the correct sequences.
I. Bombyx mori – a) Erisilk
II. Antheraea assamensis – b) Tisaarsilk
III. Antheraea mylitta – c) Mugasilk
IV. Attacus ricini – d) Mulberry silk

Answer:
a) I – d, II – c, III – b, IV – a

Question 9.
Match the silk moth with their respective leaves.
I. Bombyx mori – a) Castor
II. Antheraea assamensis – b) Arjun
III. Antheraea mylitta – c) Champa
IV. Attacus ricini – d) Mulberry


Answer:
a) I -d, II – c, III – b, IV – a

Question 10.
Find the unrelated pair regarding the silk production and its states.
a) Karnataka – Mulberry silk
b) Manipur – Muga silk
c) West bengal – Tasar silk
d) Arunachala pradesh – Muga silk
Answer:
d) Arunachala pradesh – Muga silk

Question 11.
Name the branches that involve agriculture and industry.
a) Vermiculture
b) Pisciculture
c) Sericulture
d) Poultry
Answer:
c) Sericulture

Question 12.
Life span of Bombyxmori
a) 2-3 days
b) 2 – 4 days
c) 2-5 days
d) 4 – 7 days
Answer:
a) 2 – 3 days

Question 13.
What is the number of eggs laid by Bombyx mori once?
a) 500 – 800
b) 400 – 500
c) 400 – 450
d) 600-700
Answer:
b) 400 – 500

Question 14.
What is the length of matured silkworm?
a) 7.5 cm
b) 7cm
c) 8.5 cm
d) 8 cm
Answer:
a) 7.5 cm

Question 15.
What would be the length of silk fibre in a cocoon?
a) 1000-1100 m
b) 1000-1200 m
c) 1000-1500m
d) 1000 – 1300m
Answer:
b) 1000 – 1200m

Question 16.
What is meant by mariculture?
a) Rearing of mulberry plants
b) Rearing of castor plants
c) Vermiculture
d) Apiculture
Answer:
a) Rearing of mulberry plants

Question 17.
What is meant by voltinism?
a) No of broods raised
b) Cocoon
c) Spinneret
d) None of the above
Answer:
a) No of broods raised

Question 18.
What is the ideal period for mulberry culture?
a) January, February, and November, December
b) March, April and June, July
c) June, July, and Nov, December
d) October, November and December, January
Answer:
c) June, July, and November, December

Question 19.
Find the odd one out.
a) Healthy silk moths are allowed to mate for 4 hours
b) Female lays about 400 eggs in 24 hours
c) The small larvae hatch between 7-10 days after incubation
d) The optimum temperature for rearing silk moth is 25°C – 30°C
Answer:
d) The optimum temperature for rearing silk moth is 25°C – 30°C

Question 20.
Silkmoth matured in about days
a) 40 days
b) 45 days
c) 50 days
d) 35 days
Answer:
b) 4 5 days

Question 21.
The cocoon is soaked in hot water in temperature for minutes.
a) 95°C – 97°C -10 -15 minute
b) 95°C – 97°C – 5 -10 minutes
c) 90°C – 95°C – 7 -10 minutes
d) 100°C – 105°C – 2 – 5 minutes
Answer:
a) 95°C – 97°C -10 -15 minute

Question 22.
The areas where a lot of beehives can be placed.
a) Honey culture
b) Apiculture
c) Apiaries
d) all the above
Answer:
c) apiaries

Question 23.
The nectar got from the flowers is converted into honey by the enzyme.
a) Invertase
b) Zymase
c) Lipase
d) None of the above
Answer:
a) Invertase

Question 24.
Find whether the following is true or false and find the correct sequence.
I) There is only one queen bee in a colony
II) Worker bees are around 5000 – 10000
III) The queen bee in its lifetime in 2 – 4 years lays 20 lakhs eggs.
IV) When the queen loses its fertility another worker bee becomes a queen by taking royal Jelly.
a) I – true, II – False, III – False, IV – true
b) I – true, II – False, III – true, IV – True
c) I – false, II – true, III – true, IV – true
d) I – false, II – true, III – false, IV – false
Answer:
a) I – true, II – false, III -false, IV – true.

Question 25.
How many days are needed for the worker bee to becoming mature done?
a) 15 days
b) 21 days
c) 20 days
d) 18 days
Answer:
b) 21 days

Question 26.
What is the life span of a worker bees?
a) 6 weeks
b) 5 weeks
c) 7 weeks
d) 3 weeks
Answer:
a) 6 weeks

Question 27.
What are drones?
a) a male bee from unfertilised egg
b) a female bee from fertilised egg
c) a queen bee from fertilised egg
d) a worker bee after eating royal jelly becomes a queen
Answer:
a) a male bee from unfertilised egg

Question 28.
Find the wrong pair?
a) Drone cell – Comb queen bee
b) King of honeycomb – Drone
c) Swarming – Worker bee flying with the queen bee
d) Male bee – After mating it will die
Answer:
a) Drone cell – Comb queen bee

Question 29.
Read the following statement and find the correct sequence.
I) The honeycomb is built from the abdominal secretion of a worker bee
II) The chamber of the honeycomb are hexagonal in shape
III) The young stages of honey bees accommodate the lower and central cells of the hive
IV) In Apis dorsata the brood of hive cells are similar in size and shape
a) I – false, II – false, III – true, IV – true
b) I – true, II – true, III – false, IV – false
c) I – true, II – true, III – true, IV – true
d) I – false, II – true, III – true, IV – false
Answer:
c) I – true, II – true, III – true, IV – true

Question 30.
Assertion A: The pure wax is white in colour.
Reason: B The pure wax contains carotenoids pigments.
a) Assertion A true Reason B true
b) Assertion A false, Reason B false
c) Assertion A true Reason B false
d) Assertion A false, Reason B true
Answer:
c) Assertion A true Reason B false.

Question 31.
Find the correct sequence in the following.
I) Bee wax is secreted by the abdomen of the worker bees.
II) The resinous chemical substance present in the wax is called propolis.
III) The pure wax is white in colour.
IV) The yellow of the wax is due to the carotenoid pigments.
a) I – true, II – true, III – true, IV – false
b) I – false, II – false, III – true, IV – true
c) I – true, II – false, III – true, IV – true
d) I – true, II – true, III – true, IV – true
Answer:
d) I – true, II – true, III – true, IV – true

Question 32.
Find whether the statement regarding Lac insect is true or false
I) Tachardia lacca produces lac.
II) The Lac insect is a parasite on host plant karanagalli, karuvelai
III) The female lac insects are small
IV) The female lac insects after fertilisation lays about 200 to 500 eggs
a) I – true, II – false, III – false, IV – true
b) I – true, II – true, III – true, IV – false
c) I – true, II – true, III – false, IV – true
d) I – true, II – false, III – true, IV – false
Answer:
c) I – true, II – true, III – false, IV – true

Question 33.
What is the ideal salinity for fish culture in brackish water?
a) 0.5-30ppt
b) 0.1-25ppt
c) 0.1-30ppt
d) 1-10ppt
Answer:
a) 0.5 – 30 ppt

Question 34.
Which one of the following is correct pair?
a) Exotic breed – cyprinus carpiols
b) Apiculture – Reeling
c) Seri culture – Propolis
d) Milch breed – Malvi
Answer:
a) Exotic breed – cyprinus Carpio

Question 35.
Name the exotic fishes of India.
a) Catlacatla
b) Lapeorohita
c) Cirrhina mirgala
d) Cyprinus carbeo
Answer:
d) Cyprinus carbeo

Question 36.
Name the vitamin found in fishoil?
a) A and E
b) A and D
c) A and C
d) A and K
Answer:
b) A and D

Question 37.
Ising glass is received from the part of the fish
a) Dried gills
b) Dried stomach
c) Dried air sacs
d) Dried liver
Answer:
c) Dried air sacs

Question 38.
What is the nutritive value of crustaceans?
a) Rich in glycogen protein with low-fat content
b) Rich in protein low in glycogen
c) Rich in glycogen low in fat content
d) Rich in protein and fat
Answer:
a) Rich in glycogen protein with low-fat content

Question 39.
These are freshwater prawns.
a) Penaeus indicus
b) Macrobrachium rosenbergi
c) Penaeus monodon
d) Metapenaeus
Answer:
b) Macrobrochium rosenbergi

Question 40.
What is the optimum temperature and PH for prawn culture in a hatching tank
a) 24°C – 30°C PH – 7 – 8
b) 20°C – 22°C PH -10 -12
c) 20°C – 23°C PH – 5 – 6
d) 19°C – 20°C PH – 9 -10
Answer:
a) 24°C – 30°C – PH – 7 – 8

Question 41.
Find the correct statement regarding the preparations of prawn form.
I) For algal growth, and for the subsequent stocking of prawns it is essential to drain off the water and sundry the bottom.
II) Lime should be applied to absorb excess C02 and to supply calcium which is required for moulting.
III) Fertilizers like rice, bran, poultry and cattle dung are used to increase the fertility of the soil.
IV) Preservation of prawns is done by peeling and deveining or by cooking and peeling
a) I – true, II – true, III – false, IV – false
b) I – false, II – true, III – true, IV – true
c) I – true, II – true, III – true, IV – true
d) I – true, II – false, III – true, IV – false
Answer:
c) I – true, II – true, III -true, IV – true

Question 42.
Where is pearl cultured in India for the first time?
a) Thoothukudi 1973
b) Visahapattinum 1974
c) Rameshwaram 1975
d) Kulchall973
Answer:
a) Thoothukudi 1973

Question 43.
Where are pearl oysters seen?
a) Kanyakumari coastal region a Bay of Kutch
b) Rameshwaram coastal area and Bay of Mannar
c) Nagapatinum coastal area and Thoothukudi
d) Visahapatinum coastal area and Chennai
Answer:
a) Kanyakumari coastal region a Bay of Kutch

Question 44.
The pearl oysters belongs to ‘L’ genus produce Quality pearls.
a) Gastropoda
b) Pinctata
c) Pelecypoda
d) Cephalopoda
Answer:
b) Pinctata

Question 45.
……………………….. ulturing pearl in freshwater.
a) Lamellidens
b) Mytilus
c) Loligo
d) Dentalium
Answer:
a) Lamellidens

Question 46.
The marine oysters are composed of
a) Calcium carbonate
b) Sodium carbonate
c) Potassium carbonate
d) Magnesium carbonate
Answer:
a) Calcium carbonate

Question 47.
The process of killing the silkworm cocoons is called
a) Reeling
b) Stifling
c) Spinning
d) rearing
Answer:
b) Stifling

Question 48.
Assertion A: The pearl oysters got from the sea are valuable
Reason B: The pearl oysters got from freshwater is not valuable
a) Assertion A true, B false
b) Assertion A and B reason all true
c) Assertion A false, Reason B true
d) Assertion A and Bare false
Answer:
b) Assertion A and B reason all true

Question 49.
What is the name of the breed that produces mule?
a) Outbreeding
b) Crossbreeding
c) Interspecific hybridization
d) Outbreeding
Answer:
c) Interspecific hybridization

Question 50.
Assertion X: 6 – 8 eggs can be produced by induction in an artificial method
Reason Y: The embryos at 8 – 32 celled stages are transferred to a surrogate mother.
a) Assertion x false y true
b) Assertion X true, Y false
c) Assertion X false, Y false
d) Assertion X and Y are true
Answer:
d) Assertion X and Y are true

Question 51.
Which of the cattle breed yields more milk than what they eat?
a) Vechur
b) Kankeyem
c) Gir
d) Ongole
Answer:
a) Vechur

Question 52.
Which of the following is not a milch breed?
a) Sindhi
b) Malvi
c) Jersey
d) Gir
Answer:
b) Malvi

Question 53.
Which of the following belongs to America?
a) Silkie
b) White Plymouth rock
c) Chittagong
d) Aseel
Answer:
b) White Plymouth rock

Question 54.
Name the poultry which is noted for its pugnacity?
a) Leghorn
b) Silkie
c) Brahma
d) Aseel
Answer:
d) Aseel

Question 55.
Find the odd one out
a) Leghorn – Italy
b) Chittagong – good egg yielder
c) White Plymouth rock – American breed
d) Aseel-ornamental breed
Answer:
d) Aseel – ornamental breed

Question 56.
Which among the following is a wild duck?
a) Syhlet
b) Muscori
c) Pekin
d) Mallard
Answer:
d) Mallard

Question 57.
Find the wrong statement about Duck.
a) The body is covered with oily feathers.
b) The fat layer beneath their skin prevents it from getting wet
c) They lay eggs at mid-day
d) The ducks feed on rice bran kitchen wastes and snails
Answer:
c) They lay eggs at midday

(2 marks)

II. Very Short Answer

Question 1.
What is Economic Zoology?
Answer:
Economic zoology is a branch of science that deals with economically useful animals. It involves the study of the application of animals for human welfare.

Question 2.
How are animals classified on the basis of their economic importance?
Answer:

• Animals for food and food products.
• Economically beneficial animals.
• Animals of aesthetic importance.
• Animals for scientific research.

Question 3.
Name the endemic earthworms of India.
Answer:

1. Periy ony x excavatus
2. Lampito Mauritius
3. Octo chactona serrata

Question 4.
Name the exotic species of an earthworm?
Answer:

• Eiseniafetida,
• Eudrilus eugeniae

Question 5.
Why are earthworms called ‘friends of farmers’?
Answer:
Earthworms play a vital role in maintaining soil fertility. Hence, they are called ‘friends of farmers’.

Question 6.
What decides the economic success of the industries?
Answer:

• It depends on the animals and their products.
• It depends on the proper production management and development of the next generation of farm animals.

Question 7.
What is meant by vermiculture?
Answer:
It is the process of using earthworm to decompose organic food waste into a nutrient-rich material capable of supplying necessary nutrients which help to sustain plant growth.

Question 8.
What is meant by vermicast?
Answer:
The organic matter of soil is decomposed by earthworm and becomes nutritious rich manure for plant growth.

Question 9.
What is meant by vermicompost?
Answer:
Vermicompost is composed of vermicast which contains nutrients plant growth promoters and organic matters.

Question 10.
What is meant by vermitech?
Answer:
The application of earthworm in the technology of composting and bioremediation of soil and other activities is called vermitech.

Question 11.
What are the pests of earthworms?
Answer:
Ants, springtails, centipedes, slugs, mites, certain beetle larvae, birds, rats, snakes, mice, toads and other insects or animals which feed on worms.

Question 12.
What are the special characters of vermicompost?
Answer:

• Aeration
• draining of water
• retains water.

Question 13.
What is meant by vermiwash?
Answer:

• Vermi wash is a liquid collected after the passage of water through a coloumn of vermibed.
• It is useful as foliar spray to enhance plant growth and field.

Question 14.
What is sericulture?
Answer:
Sericulture is an agro-based industry which denotes commercial production of silk through silkworm rearing.

Question 15.
What is meant by sericulture?
Answer:
Sericulture denotes commercial production of silk through silk worm rearing.

Question 16.
What is meant by moriculture?
Answer:
The cultivation of mulberry plant which is used as a food for silk worm is called moriculture.

Question 17.
Which is the suitable period for mulberry cultivation?
Answer:
June, July, November, and December

Question 18.
What are the stages involved in rearing process of silk worm?
Answer:
Disinfection of rearing house Incubation of eggs Brushing, young larval rearing Late age larval rearing.

Question 19.
What is meant by stifling?
Answer:
The process of killing the cocoon is called stifling.

Question 20.
What is meant by reeling?
Answer:
The process of removing the threads from the killed cocoon is called reeling.

Question 21.
What is cooking?
Answer:
The process of soaking cocoons in hot water (95° – 97°) for 10 – 15 minutes to soften the gum that binds the silk threads together is called cooking.

Question 22.
What are Uzi files?
Answer:
These files which can attack silkworm.

Question 23.
What is meant by cooking?
Answer:
The cocoons are soaked in hot water at 95° – 97°c for 10 -15 minutes to soften the gum that binds, the silk threads together are called cooking.

Question 24.
What is spun silk?
Answer:
The silk produced from silk wastes used for producing spun silk.

Question 25.
What are apiaries?
Answer:
They are areas where a lot of beehives can be placed.

Question 26.
Name the bees used for Apiculture.
Answer:

• Apis dorsata – Rock bee
• Apis florea – Little bee
• Apis indica – Indian bee
• Apismellifera – European bee
• Apis adamsoni – African bee

Question 27.
Name the types of beehives which are in practice in India?
Answer:

• Langstroth
• Newton

Question 28.
What is meant by swarming?
Answer:
The mass emergence of larvae of Lacinsect from the egg in search of a host plant is called swarming.

Question 29.
What is meant by nuptial flight?
Answer:
A unique flight that takes place by the queen bee followed by several drones is called “nuptial flight”.

Question 30.
Which is called as king of the colony? Why is called so?
Answer:
The king of colony is drone hence the sole duty of the drone is to fertilize the vergin queen.

Question 31.
Name the sugar component present in the honey?
Answer:
levulose, dextrose maltose.

Question 32.
What are the uses of honey?
Answer:

• It is used as an antiseptic
• Laxative
• Sedative
• It is used in the preparation of cakes bread and biscuits.

Question 33.
What is meant by Lac culture?
Answer:
The culture of lac insect using techniques for the procurement of Lac on large scale is known as Lac culture.

Question 34.
Name the host plants on which Lac insects live?
Answer:
Karanagalli – Acacia catechu Karuvelai – Acacia nilotica Kumbadiri – Schleichera oleosa.

Question 35.
What is meant by hyper parasitism?
Answer:

• Hyper parasitism is a condition in which a secondary parasite develops within a previously existing parasite.
• The caterpillars feed upon lac insects showing hyper – parasitism.

Question 36.
What is meant by inoculation?
Answer:
The process of introducing lac insects to the host plant is called inoculation.

Question 37.
What is meant by Harvesting?
Answer:
The collection of Lac from the host plant is known as harvesting.

Question 38.
What is meant by ‘Arilac’?
Answer:
The Immature lac insects produce a lac which is called ‘arilac’.

Question 39.
What is meant by sticklac?
Answer:
Lac cut from the host plant is called ‘stick lac’.

Question 40.
What is seed Lac?
Answer:
The Lac scraped collected grounded and the dust particles are removed to produce a lac called seedlac.

Question 41.
What is meant by Shellac?
Answer:
The seedlac is sundried and then melted to produce “Shellac”.

Question 42.
What is meant by aqua ponies?
Answer:
Aquaponics is a technique which is a combination of aquaculture and growing plants in non – soil media and nutrient-laden water.

Question 43.
What are the organisms farming through aqual culture?
Answer:
Fish molluscs crustaceans and aquatic plants are farming through aquaculture.

Question 44.
How aquaculture is classified on the basis of it source?
Answer:

• Freshwater aquaculture
• Brackish water aquaculture
• Marine water aquaculture.

Question 45.
What is meant by Brackish water culture?
Answer:
Culturing of animals in the water having salinity range 0.5 – 30ppt are called brackish water cultures.

Question 46.
Name the fishes cultured through brackish water culture?
Answer:
Milkfish, Sea bass, Grey mullet Kari meen.

Question 47.
What is meant by metahaline culture?
Answer:
Culturing of animals in the salinity ranges from 36 – 40o% is called metahaline culture (eg) Artemia salina.

Question 48.
What are the organisms rearing through aquaculture?
Answer:

1. Molluscs
2. Aquatic plants
3. Crustaceans

Question 49.
Give notes on fishes of brackish water?
Answer:
Brackish water fishes spend most of its life in river mouths backwaters mangrove swamps and coastal lagoons.

Question 50.
What is meant by mariculture?
Answer:
Culturing of animals in the water salinity ranges from 35- 35% is called mariculture.

Question 51.
Give short notes on Artemia salina?
Answer:
It is a metahaline organism. It lives in high saline waters because of its high osmoregulatory capacity.

Question 52.
What is meant by composite fish culture?
Answer:
Few selected fishes belonging to different species are stocked together in proper proportion in the pond is called composite culture.

Question 53.
What are the organisms cultured through composite fish culture?
Answer:

• Catla Catla
• Labeo rohita
• Cirrhina mirgala.

Question 54.
What is meant by exotic fish culture?
Answer:
The fishes imported in to a country for fish culture are called exotic fishes and such fish culture is known as exotic fish culture.

Question 55.
Name the exotic fishes cultured in India?
Answer:

• Cyprinus carpio
• Oreochromis mossambicus.

Question 56.
What is meant by fish meal?
Answer:
Fish meal is prepared from fish waste after extracting oil from the fish.

Question 57.
What is meant by Ising glass?
Answer:

• Ising glass is high-grade collagen produced from dried air bladder.
• It is used for clarification of wine beer and vinegar.

Question 58.
What is meant by outbreeding?
Answer:
It is the breeding of unrelated animals. They do not have common ancestry for 4-6 generations.

Question 59.
What is the use of outbreeding?
Answer:
Outbreeding helps to produce hybrids with superior qualities and helps to create new breeds. New and favourable genes can be introduced into a population through outbreeding.

Question 60.
What is meant by outcrossing?
Answer:
It is the breeding between unrelated animals of the same breed but having no common ancertry.

Question 61.
What is meant by artificial insemination?
Answer:
Artificial insemination is a technique in which the semen collected from the male is injected to the reproductive tract of the selected female.

Question 62.
What is meant by recovery period?
Answer:
Nucleated oysters are attached with floating rafts suspended into a depth of 2 to 3 metres for about 6 to 7 days is called the recovery period.

Question 63.
What is the composition of pearl?
Answer:

• Water-2-4%
• Calcium carbonate-90%
• Organic matter-3.5-5.9%
• residue-0.1-0.8%

Question 64.
Name the species of prawn?
Answer:
Penaues indicus, Penaeus monodon, Metapenaeus dobsoni, Macrobrachium rosenbergil.

Question 65.
Where are pearl oysters cultured?
Answer:
Kanyakumari Bay of Kutch.

Question 66.
What is meant by Linga pearl or best quality pearl?
Answer:
The pearl oysters in habit the ridges of rock-forming extensive pearl banks. These pearl beds produce the best quality of pearl or Linga pearl.

Question 67.
What are the types of cultivable fish?
Answer:

• Indigenous or native freshwater fish. (cg) Catla, Labeo
• Saltwater fishes acclimatized for freshwater.
• Exotic fishes or imported from other countries. (eg) Common Carps.

Question 68.
What is Hapa?
Answer:
Hatching hapas are rectangular through shaped tanks made up of mosquito net cloth supported by bampoo poles and fixed in the river.

Question 69.
What are the advantages of composite fish farming?
Answer:

•  All available niches are fully utilized.
• Compatible species do not harm each other.
• No competition among different species.

Question 70.
What is meant by animal husbandry?
Answer:
Animal husbandry is the practise of breeding and raising livestock cattle like cows, buffaloes goats and birds that are useful to human beings.

Question 71.
What is meant by breed?
Answer:
A group of animals related by descent and with similar characters like general appearance features size etc as said to belong to a breed.

Question 72.
How can we classify cattle on the basis of their utility?
Answer:

1. Milch breeds
2. Draught purpose breeds
3. Dual-purpose breeds.

Question 73.
What are characteristic features of healthy cattle?
Answer:

• They appear bright
• Alert
• Active
• Shiny coat.

Question 74.
What are the characteristic features of unhealthy cattle?
Answer:

• They appear dull
• Restless
• Change posture frequently with a drop in milk yield.

Question 75.
Name the important cattle disease?
Answer:

• Rinder pest
• Cowpox
• Anthrax
• hemorrhagic fever.

Question 76.
What is meant by poultry?
Answer:
It is the rearing and propagation of chicken ducks turkeys geese quail and guinea fowls.

Question 77.
What are the types of chicken breeds based on their utility?
Answer:

• They are egg layers
• Broiler type
• Dual type
• Games and
• ornamental types.

Question 78.
Name the native ducks.
Answer:

• Indian Runner
• Syhletmeta.

Question 79.
Name the exotic ducks.
Answer:

• Muscari
• Pekin
• Aylesbury
• Campbell

Question 80.
What are the three stages of sericulture?
Answer:

1. Cultivation of food plants for the silkworm.
2. rearing of silkworm.
3. reeling and spinning of silk.

Question 81.
What is meant by apiculture?
Answer:
Care and management of honey bees on a commercial scale for the production of honey is called apiculture.

Question 82.
What is the importance of aquaponics?
Answer:
It maintains the ecosystem balance by recycling the waste and excretory products produced by the fish.

Question 83.
What is meant by aquaponics?
Answer:
Aquaponics is a technique which is a combination of aquaculture and growing plants in non-soil media and nutrient-laden water.

Question 84.
Based on the water resources where are aquatic organisms cultured? Give examples.
Answer:

1. Freshwater culture
2. Brackish water culture, Marine culture, Cultured organism, Fishes, Prawns, Crabs and oysters.

Question 85.
What are the objectives of animal breeding?
Answer:

• To improve growth rate
• enhancing the production of milk meat egg etc.
• Increasing the quality of the animal products
• Improved resistance to disease.
• Increased reproductive rate.

3 marks

III. Short answers

Question 1.
What is meant by vermiculture?
Answer:
It is the process of using earthworm to decompose organic food waste into a nutrient-rich material capable of supplying necessary nutrients which help to sustain plant growth.

Question 2.
What is meant by worm casting?
Answer:
The worm castings are pure worm waste and nutrient-rich organic soil and composed of castings, bits of bedding, and other organic matter.

Question 3.
Why earthworms are called as ‘Farmers of friends’
Answer:

• They support bacteria fungi which are essential for sustaining healthy soil.
• The breakdown of organic matter by the activity of the earthworms.
• It increases porosity aeration, drainage of the soil.

Question 4.
What are the three main components of sericulture?
Answer:

1. Cultivation of food plants for the silkworms.
2. Rearing of silkworms.
3. Reeling and spinning of silk.

Question 5.
Name the predators of earthworms?
Answer:

• Ants,
• centipedes,
• Slugs,
• Birds,
• Rats,
• Snakes.

Question 6.
Name the honey bees used in apiculture.
Answer:

• Apis dorsate,
• Apis florea
• Apis indica
• Apis mellifera
• Apisadamsoni

Question 7.
Whatisprobolis?
Answer:
The wax is masticated and mixed with the secretions of the cephalic glands to convert it into a plastic resinous substance called probolis.

Question 8.
What are the uses of silk?
Answer:
Uses of Silk:-
1. Silk fibers are utilized in preparing silk clothes. Silk fibers are now combined with other natural or synthetic fibers to manufacture clothes like Teri-Silk, Cot-Silk etc. Silk is dyed and printed to prepare ornamented fabrics. They are generally made from Eri-silk or spun silk.

2. Silk is used in industries and for military purposes.

3. It is used in the manufacture of fishing fibers, parachutes, cartridge bags, insulation coils for telephone, wireless receivers, tyres of racing cars, filter fibres, medical dressings, and suture materials.

Question 9.
Describe the structure of Beehive?
Answer:

• The house of honey bees is a beehive.
• The hive consists of hexagonal cells made up of wax secreted by the abdomen of a worker bee.

• These hives are found hanging vertically from the rocks. building or branches of trees.
• The young stages of honey bee accommodate the lower and central cells of the hive.
• In the rock bees hives there are separate cells for queens, worker and drones.

Question 10.
Explain the structure of a beehive?
Answer:
Structure of a Bee Hive. The house of honey bees is termed a beehive or comb. The hive consists of hexagonal cells made up of wax secreted by the abdomen of worker bees arranged in opposite rows on a common base. These hives are found hanging vertically from the rocks, buildings or branches of trees. The young stages of honey bees accommodate the lower and central cells of the hive called the brood cells.

In Apis dorsata, the brood cells are similar in size and shape but in other species, brood cells are of three types viz., queen cell for queens, worker cell for workers, and drone cells for drones. The cells are intended for the storage of honey and pollen in the upper portion of the comb whereas the lower portions are for brood rearing.

Question 11.
What is meant by inbreeding? What are its effects?
Answer:
Breeding between animals of the same breed for 4 – 6 generations is called inbreeding.
Effects:

1. It increases homozygosity.
2. Exposes the harmful recessive genes.
3. Reduces fertility.
4. It produces inbreeding depression.

Question 12.
How animals are classified based on their economic importance.
Answer:

• Animals for food and food products.
• Economically beneficial animals.
• Animals of aesthetic importance.
• Animals for scientific research.

Question 13.
Give an account of earthworm based on their habitat.
Answer:
First group:

• The humus formers dwell on the surface and feed on organic matter.
• They are darker in colour.
• These worms are used for vermicomposting.

Second group:
The humus feeders are burrowing worms that are useful in making the soil porous and mixing and distributing humus throughout the soil.

Question 14.
What are the uses of honey wax?
Answer:

• It is used for making candles.
• It is used for making waterproofing materials.
• It is used for making home appliances polishes for leather.
• It is used in pharmaceutical industries.

Question 15.
What is meant by Hyper parasitism?
Answer:
A condition in which a secondary parasite develops within a previously existing parasite.

Question 16.
What are the economic importance of Lac?
Answer:

• It is used as sealing wax.
• It is used as a good insulator.
• It is used in preparations of shoe and leather polishes.
• It is a protective coating of wood.
• It is used in preparation of plastic moulded articles.
• It is used as filling material for gold ornament.

Question 17.
Name the breeds of cattle?
Answer:

• Milch breeds – Sindhi Jersey
• Draught breeds – KangeyamMalvi
• Dual-purpose breeds – Ongole Hariana

Question 18.
What is meant by Milch breed?
Answer:
They are high milk yielders with extended lactation. (eg) Sindhi, brown swiss.

Question 19.
What is Dual purpose?
Answer:
Cows are meant for yielding more milk and bullocks are used for better drought purpose, (eg) Ongole Hariana

Question 20.
What is draught purpose breeds?
Answer:
Bullocks are good for draught purposes (eg) Malvi.

Question 21.
What are the characteristic features of healthy cattle?
Answer:
A healthy animal eats drinks and sleeps well regularly.
Healthy cattle appear bright.
Alert and active in their movement with a shiny coat.

Question 22.
What are the external factors affecting fish culture?
Answer:

1. Temperature,
2. Light,
3. Rain,
4. Flood,
5. Water current,
6. Turbidity of water,
7. pH

Question 23.
What is Aquaponics?
Answer:
Aquaponics is a technique which is a combination of aquaculture (growing fish)’ and hydroponics (growing plants in non-soil media and nutrient-laden water).

Question 24.
Name the species of prawn.
Answer:

• Penaeus indicus,
• Penaeus monodon,
• Metapenaeus dobson,
• Macrobrachium rosenbergii.

Question 25.
What are the three types of aquaculture on the basis of the source?
Answer:
On the basis of source, aquaculture can be classified into three categories. They are

1. Freshwater aquaculture
2. Brackish water aquaculture
3. Marine water aquaculture.

Question 26.
What are the benefits of poultry farming?
Answer:

• It does not require high capital for the construction and maintenance of poultry farming.
• It does not require a big space.
• It ensures the high return on investment.
• It provides fresh and nutritious food and has a huge global demand.
• It provides employment opportunities for the people.

Question 27.
What are the uses of dairy products?
Answer:

• Milk is a rich source of vitamin A, B₂, B₁
• It is a complete food for infants.
• Dairy products such as yoghurt cheese butter ice cream condensed milk, milk powder are produced from milk.

Question 28.
What is the importance of meat?
Answer:

• Meat is rich in protein.
• It also contains minerals like iron zinc vitamins and selenium.

Question 29.
What is Mariculture?
Answer:
Culturing of animals in the water salinity ranges from 30 – 35% is called Mariculture. Some fishes like Chanos sp, Mugil cephalus are cultured here.

Question 30.
What are poultry diseases?
Answer:
Ranikhet, Coccidiosis, Fowl pox.

5 Marks

IV. Give Detailed Answers

Question 1.
How are vermicompost produced?
Answer:
Types of Movements:

• Vermicompost is the compost produced by the action of earthworm in association with all other organisms in the compost unit.
• Vermicompost bed may be selected on upland or an elevated level.
• We have to construct a cement pit of 3 x 2 x 1m size over the ground surface using bricks.
• The vermibed should not be exposed to direct sunlight.
• The first layer of vermibed contains gravel at about 5 cm in height followed by coarses and to a thickness of 3.5 cm which will facilitate the draniage of excess water.
• The unit can now be loaded with digested biomass or animal dung.
• Earthworms such as periyonyx excavatus Eisenia fetida or Eudrilus eugeniae are introduced on the top.
• Earthworms release their castings on the surface.
• Vermiwash is a liquid collected after the passage of water through a column of vermibed. It is useful as a foliar spray to enhance plant growth.

Question 2.
Describe the life cycle of bombyx mon?
Answer:

• This moth is unisexual.
• Just after emergence male moth copulates with females for 2-3 hours.
• Just after copulation female starts laying about 400-500 eggs.
• The eggs after ten days of incubation hatch into larva called a caterpillar.
• The newly hatched caterpillar is about 3mm in length and is pale yellowish-white colour.
• The mandibulate type of mouthparts adapted to feed easily on the mulberry leaves.

• After 1st, 2nd, 3rd and 4th moulting caterpillars get transformed into 2nd, 3rd, 4th and 5th instars respectively.
• It develops salivary glands, stops feeding and undergoes pupation.
• The cafter pillars stop feeding and moves towards the comer among the leaves and secrete a sticky fluid through their silk gland.
• The secreted fluid comes out through spinnerret which hardens on exposure to air and is wrapped around the body of cater pillar in the forms of a covering called a cocoon.
• The length of continous thread secreted a caterpillar for the formation of cocoon is about 1000 -1200 metres.
• The pupal period lasts for 10-12 days and the pupae cut through the cocoon and emerge into adult moth.
• In larvel stages the larvae moults for 3 or 4 times or 5 times and become a matured moth.

Question 3.
What are the uses of vermicompost?
Answer:

• Vermicompost is rich in essential plant nutrients.
• It improves soil structure texture aeration and water holding capacity and prevents soil erosion.
• Vermicompost is rich in nutrients and an eco-friendly amendment soil for farming and terrace gardening.
• It enhances seed germination and ensures good plant growth.

Question 4.
What are the reasons for culturing carps in India?
Answer:
Major carps have proved to be best suited for culture in India because the carps

1. Feed on zooplankton and phytoplankton, decaying weeds, debris, and other aquatic plants.
2. They can survive in turbid water with slightly higher temperatures.
3. Can tolerate O₂ variations in water.
4. Can be transported from one place to another easily.
5. They are highly nutritive and palatable.

Question 5.
What are the uses of silk?
Answer:

• Silk fibres are utilized in preparing silk cloths.
• Silk fibres are combined with natural or synthetic fibres to manufacture Teri – silk and cot silk.
• Silk is dyed and printed to prepare ornamental fabrics.
• Silk is used in industries and for military purposes.
• It is used in the manufacturing of fishing fibres, parachutes insulation coils for telephones.
• They are used in the preparation of tyre of racing cars, filter fibres in medical dressings and as suture materials.

Question 6.
Name the pests and diseases of the silkworm.
Answer:
1. Predators:
They feed on silkworms.

• Birds,
• ants,
• crows,
• kites,
• rats.

2. Diseases:

• Pebrin – It is a disease caused by protozoa Nosema bombycis.
• Flacherie – It occurs in the mature larvae caused by bacteria like streptococcus and staphylococcus.
• Grasserie – It is aviral disease caused by Bombyx mori nuclear polyhedrosis virus.
• White Muscardine – It is caused by fungus Beauveria bassiana.

Question 7.
Describe the social organziation of honey bee.
Answer:

• In honey bee a highly organized division of labour is found.
• There are three type of honey bees seen in the colony.
• There are one queen 10000 – 30000 workers and few hundred drones in a colony.

Queen bee:

• It feeds on royal Jelly.
• It is only function is to lay eggs throughout its life span.
• During breeding season in winter, a unique flight takes place by the queen bee followed by several drones is called nuptial flight.
• After mating the queen bee lays about 15 lakh eggs in two to four years.

Worker bee:

• These are sterile females.
• Worker bee lives in a worker well and it takes, about 21 days to develop from the egg to adult, and its life span is about six weeks.

Works:

• It secretes royal Jelly.
• Prepares bee – bread to feed the larvae.
• Takes care of the queen and drones.
• Secretes bee wax.
• In last three weeks she searches and gathers the pollen nectar.

Drones:

• The drone develops from an unfertilized egg.
• It lives in a chamber called a drone cell.
• The only duty of the drone is to fertilize the queen and it is called as the king of the colony.

Question 8.
Describe the structure of the Langstroth beehive?
Answer:

• Stand – It is a basal part of the hive and are adjusted to make a slope for rainwater to drain.
• Bottom board – It is situated above the stand. It has two gates one gate is an entrance the other acts as an exit.
• Brood chamber – It is an important part of the hive. It is provided with 5 to 10 frames arranged one above the other through which the workers can easily pass.
• The frame is composed of wax – sheet which is held in a vertical position up by a couple of wires.
• It is strong that can be used repeatedly.
• Super – It is a chamber without cover and base. It is provided with many frames to provide additional space for expansion of the hive.
• Inner cover – It is a wooden piece used for covering the super with many holes for proper ventilation.
• Top cover – It is meant for protecting the colonies from rains. It is covered with a sheet which is plain and sloping.

Question 9.
Give an account of equipments of beehives and its uses.
Answer:

• Queen Excluder – It is utilized to prevent the entry of queen bee from the brood chamber into the super chamber.
• Comb foundation – It is a sheet of bee wax.
• Bee gloves – They are used by keepers for protecting their hands.
• Bee veil – It is a device to protect the beekeeper from a bee sting.
• Smoker – It is used to scare the bees during honey collecting.
• Hive Tool – It helps in scraping excess propolis or wax.
• Un capping knife – It helps in removing the cap from the combs.
• Bee brush – It is used to brush off bees from honeycombs.
• Queen introducing cage – It is made of wire nets used for keeping the queen for 24 hours with worker bees.
• Feeder – It is a basin with sugar syrub covered by grass to feed the bees during the drought season.
• Honey extractor – This spins the combs rapidly to extract honey.
• Hive entrance guard – It is a device which prevents the escape of the queen during the warming season.

Question 10.
Describe the process of rearing silkworms?
Answer:

• A typical rearing house 6 m x 4m x 3.5m is constructed on an elevated place under shade to accommodate 100 dfls.
• The windows and ventilators should be covered with a nylon net to restrict the entry of uziflies and other insects.
• The selected healthy silk moths are allowed to mate for 4 hours.
• The female moth is kept in a dark plastic bed it lays about 400 eggs in 24 hours.
• The small larvae hatch between 7 – 10 days.
• The larvae are kept in trays at a temperature of about 20°C-25°C.
• As the larvae grow they are transferred to fresh leaves on clean trays.
• Their maturity is achieved in about 45 days.
• At this stage the salivary glands start secreting silk to spin cocoons.

Question 11.
What is meant by aquaponics? Describe its methods?
Answer:
1. Deepwater culture – Aquaponics is a technique which is a combination of aquaculture and growing plants in non – soil media.

• It is a raft-based method.

• In this method, the raft floats in water plants are kept in the holes of the raft and the root floats in water. Fast-growing plants are cultivated.

2. Media-based method – It involves growing plants in inert planting media likely pellets or shales.
This method is applicable for home and hobby scale system. Large number of fruiting plants leafy green plants herbs can be cultivated.

3. Nutrient film technique – It involves the passage of nutrient-rich water through a narrow trough or pvc pipe.
Plants are kept in the holes of the pipe to allow the roots to be in free contact with the water stream.

4. Aquavertica or vertical aquaponics – Plants are stacked in top of each other in tower systems.
This method is suitable for growing leafy green, strawberries and crops that do not need supporting solid substratum to grow.

Question 12.
Describe the structure of honey bee hive?
Answer:

• The house of honey bee is termedas bee hive or comb.
• The hive consists of hexagonal cells made up of wax secreted by the abdomen of worker bee arranged in opposite rows on a common base.
• These hives are found hanging vertically from the rocks building or branches of trees.
• The young stages of honey bees accomodate the lower and central cells of the hive called the brood cells.
• There are separate cells for queen. Drones and workers.
• In the upper portion of the comb honey and pollen are stored.
• In the lower portion are for brood rearing.

Question 13.
What is Natural breeding of fishes?
Answer:
Natural breeding (Bundh breeding): These are special types of ponds where natural riverine conditions or any natural water resources are managed for the breeding of culturable fishes. These bundhs are constructed in large low-lying areas that can accommodate large quantity of rainwater. The shallow area of such bundhs is used as a spawning ground.

Question 14.
What are the characteristic features of cultivable fishes.
Answer:

• Fishes should have high growth rate in short period for culture.
• They should accept a supplementary diet.
• They should be hardly enough to resist some common diseases and infection of parasites.
• Fishes proposed for polyculture should be able to live together without interferring or attaching other
  fishes.
• They should have high conversion efficiency so that they can effectively utilize the food.

Question 15.
Why carps have proved to be best suited for culture in India?
Answer:

• Feed on zooplanktons and phytoplanktons decaying weeds debris and other aquatic plants.
• They can survive in turbid water with slightly higher temperatures.
• Can tolerate O₂ variations in water.
• Can be transported from one place to another easily.
• They are highly nutritive and palatable.

Question 16.
Give an account of induced breeding.
Answer:

• To improve the quality of fish seed by the artificial method of fertilization is developed.
• The gonadotrophin (FSH+ LH) secreted by the pituitary gland influences the maturation of gonads and spawning in fishes.
• The pituitary gland is removed from a healthy mature fish.
• The pituitary extract is prepared by homogenizing in 0.3% saline and centrifuged for 15 minutes at 8000rpm.
• The supernatant is injected at the base of the caudal fin.
• Male and Female fishes start to releasing gametes and are fertilized.

Question 17.
What are the types of prawn fishery?
Answer:

1. Shallow water prawn fishery – This is located on the west coast restricted to shallow waters.
2. Estuaries prawn fishery – In the backwater areas of the western coast, Ennur pulicat chilka lake and Estuaries of Ganga and Brahmaputra culture is done.
3. Freshwater prawn fishery – Prawns are caught from the rivers and lakes throughout India.
4. Marine prawn fishery – Prawn belongs to the family, penaeidae are caught along the Indian coast.

Question 18.
Give an account of the culture of freshwater prawns?
Answer:

• Macrobrachium rosenbergii is seen in rivers fields and low – saline estuaries.
• For fertilization, one pair of prawn are kept in a separate tank.
• After mating the eggs are laid.
• Temperature 24°C – 30°C and PH 7-8 should be maintained in the hatching tank.
• The hatched larvae are supplied with artificial feed.
• Young ones 5cm length can be reared in fresh or slightly brackish water ponds and harvesting of prawns can be done twice a year.

Question 19.
What are the methods of animal breeding?
Answer:
Methods of Animal breeding:
There are two methods of animal breeding, namely inbreeding and outbreeding:

1. Inbreeding: Breeding between animals of the same breed for 4-6 generations is called inbreeding. Inbreeding increases homozygosity and exposes the harmful recessive genes.

Continuous inbreeding reduces fertility and even productivity, resulting in “inbreeding depression”. This can be avoided by breeding selected animals of the breeding population and they should be mated with superior animals of the same breed but unrelated to the breeding population. It helps to restore fertility and yield.

2. Outbreeding: The breeding between unrelated animals is called outbreeding. Individuals produced do not have common ancestors for 4-6 generations.

Outbreeding helps to produce new and favourable traits, to produce hybrids, with superior qualities, and helps to create new breeds. New and favourable genes can be introduced into a population through outbreeding

Question 20.
What are the types of cultivable fish Types of cultivable fishes?
Answer:
Types of Cultivable fishes:

• Indigenous / Native freshwater fishes, (eg) Major Carps Catla Labeo Clarias.
• Saltwater fishes acclimatized for freshwater. (eg)Chanos, Mullet
• Exotic fishes. Imported from other countries, (eg) Common Carps.

Characteristic features of Carps:

• Feed on Zooplanktons and phytoplanktons decaying weeds debris and other aquatic plants.
• They can survive in turbid water with slightly higher temperatures.
• Can tolerate 0₂ variations in water.
• Can be transported from one place to other.
• They are highly nutritive and palatable easily

Question 21.
Give an account of the management of fish farms?
Answer:
To culture fish one should have an idea about different stages of fish culture such as topographic situation quality source physical-chemical and biological factors of water.
Stages of fish farming:
Breeding Pond:
The first step in fish culture is the breeding of fishes therefore for proper breeding special types of ponds are prepared called breeding ponds. These ponds are prepared near the rivers of natural water resources.
a) Natural breeding:
These bundhs are constructed in large low-lying areas that can accommodate a large quantity of rainwater.
b) Induced breeding:

• This involves the removal of ova and sperm from female and male by artificial mechanical process and the eggs are fertilized.
• The fertilized eggs are removed from the spawning place and kept in hatching hapas. Fish seeds: The fish seed is collected from breeding ponds and transferred to the hatching pits.

3. Hatching Pit:
The fertilized eggs are kept in hatching pits. The hatching pits should be nearer to the breeding grounds should be smaller in size with good quality water.
There are two types of hatching pits:

1. Hatcheries: These are small-sized ponds in which unfertilized eggs are transferred and hatching happens.
2. Hatching hapas: These are rectangular trough-shaped tanks made up of mosquito net cloth supported by bamboo poles and fixed in the river.

4. Nursery Pond:
The newly hatched fries are transported from the hatching happa to nursery ponds where they grow into fingerlings.

5. Rearing Pond:
This pond is long and narrow and this pond should be free from toxicants and predators. The fingerlings are transferred to the stocking ponds.

6. Stocking Ponds:

• This pond should be devoid of weeds and predatory fishes.
• Proper organic manuring should be done to the production with cow dung.

7. Harvesting:

• Well-grown fishes are taken out for marketing is harvesting.
• Small-sized fishes are again released into the stocking ponds for further growth.
• The harvested fishes are preserved and then marketed.

Question 22.
a) What is meant by composite fish farming?
b) What are the significance?
c) What are the fishes cultured through composite fish farming.
Answer:
a. Composite fish farming: Few selected fishes belonging to different species are stocked together in proper proportion in a pond is called composite fish farming.

b. Merits :

• All available niches are fully utilized.
• Compatible species do not harm each other.
• No competition among different species is found.

c. Fishes that are cultured :

• Catla Catla
• Labeo rohita
• Cirrhinus mrigala

Question 23.
Give an account of the economic importance of fish.
Answer:
1. Fishes form a rich source of protein food the sardines, mackerel tuna herrings have high amino acid concentrations.
2. These fishes have histidine and omega falty acids.
3. Minerals such as calcium magnesium phosphorus potassium and copper and present.
a) Fish Oil:

• It is an important fish product it is derived from fish liver and from the fish body.
• This is rich in vitamin A and O and iodine.
• It is used in the manufacture of laundry soap paints and cosmetics.

b) Fish Meal:

• It is prepared from fish waste after extracting oil from the fish.
• These dried wastes are used to prepare food for pig, poultry and cattle.
• The wastes obtained during the preparation of fish meal are used as manure.

c) Ising glass:

• It is high-grade collagen produced from dried air bladder of cat fish and carps.
• It is used for clarification of wine beer and vinegar.

Question 24.
Give notes on
a) Pearl Culture
b) Formation of pearl.
Answer:
a) Pearl Culture:

• Pearl is a white shining globular concretion found within the shell of an oyster.
• In India it was cultured for the first time in 1973 at Thoothukudi.
• High-quality pearls are obtained from Genus Pinctada that can be cultured in the salinity range of 30 ppt in racks raft and long-line method.
• The pearl oysters in habit the ridges of rocks or dead coral forming the best quality pearl.

b) Pearl Formation:

• When a foreign particle accidentally enters into the space between the mantle and shell of the oysters it adheres to the mantle.
• The mantle epithelium encloses its likes sac and starts to secrete concentric layers of nacre around it as a defensive mechanism.
• The repeated layers of calcium carbonate make the hard and glossy pearl that are separated and graded.

Question 25.
Give an account of artificial pearl culture?
Answer:

• Oysters are caught by a special type of cages.
• This cage is dipped into a sand cement mixture providing a rough surface to the cages and are suspended at a depth of 6 meters.

2. Rearing of oysters:

• The collected oysters are placed into the culture cages for a period of 10 – 20 days.
• These cages are protected from enemies like octopus, Eel and devil fishes.

3. Insertion of nucleus:
a) Fitness of oysters for operation:
The selected oysters for the insertion of nucleus should be healthy and strong enough to overcome the stress during operation.
b) Preparation of graft tissues:

• The piece of tissue which is inserted inside the mantle is called as “graft” tissue.
• It is essential to keep the outer surface in contact with the inserted nucleus as nacre secreting cells are found only on the outer surface.

c) Preparation of nucleus:

• Any small particle may function as a nucleus to initiate pearl formation.
• If it is calcareous the deposition of nacre was found to be more on the calcareous nucleus.

d) Insertion of the nucleus:
For the insertion of nucleus, oysters are fixed in a desk clamb and mantle folds are smoothly touched to expose the foot followed by an incision into the epithelium of the foot and the nucleus is inserted.

e) Post Operation Care:

• Nucleated oysters are placed into cages and suspended into 2-3 metres of depth for 6-7 days.
• These periods are known as “Recovery Period”.
• These oysters are kept for 3-6 years undisturbed.

f) Harvesting of Pearl:
After the completion of 3 years pearl oysters are harvested. It is usually done during December to February.

g) Clearing of Pearls:
After taking out the pearls from the oyster’s shell. They are washed properly cleared with the soap solution.

Question 26.
What is inbreeding? What are its merits and demerits?
Answer:
Breeding between animals of the same breed for 4-6 generations is called inbreeding.
Merits:

• It increases homozygosity.
• It exposes the harmful recessive genes. Demerits:

1. Continuous inbreeding reduces fertility
2. And results in inbreeding depression. Avoiding inbreeding depression:
This can be avoided by breeding selected animals be mated with superior animals of the same breed but unrelated to the breeding population.

Question 27.
What is Dairying and Dairy Operation?
Answer:
Dairying is the production and marketing of milk and its products. The dairy operation consists of proper maintenance of cattle, the collection, and processing of milk, and its by-products.

Question 28.
What are the types of outbreeding?
Answer:
1. Out Crossing:
It is the breeding between unrelated animals of the same breed but having no common ancestry.
Out Cross: This method is suitable for breeding animals that are below average in productivity.

2. Crossbreeding:

• Breeding between a superior male of one breed with a superior female of another breed.
• The cross-breed progeny has superior traits. This is called hybrid vigour or heterosis.

3. Interspecific hybridization:

• Mating between male and female of two different species.
• The progeny obtained from such crosses are different from their parents.
• Mule is produced by the crosses between male donkey and a female horse.

Question 29.
Give an account of Multiple Ovulation embryo transfer technology? MOET.
Answer:
MOET:

• This method is applied when the success rate of crossing is low even after artificial insemination.
• In this method, the follicle-stimulating hormone is administered to cows for inducing follicular maturation and superovulation.
• Instead of one egg per cycle, 6-8 eggs can be produced.
• The eggs are carefully recovered non-surgically from the genetic mother and fertilized artificially.
• The embryos at the 8 – 32 celled stage are recovered and transferred to a surrogate mother.
• This technology can be applied to cattle sheep and buffaloes.
• It can produce high milk-yielding females and high-quality meat-yielding bulls in a short time.

Question 30.
a) What is meant by dairying?
b) Classify them on the basis of their utility.
c) Give an account of dairy products.
Answer
a) Dairying:

• It is the production and marketing of milk and its products.
• The dairy operation consists of maintenance of cattle the collection, processing of the milk, and its by-products.
• These are 26 well-defined breeds of cattle and 6 breeds of buffaloes in India.

b) Classification of Cattle

1. Dairy breeds: They are high milk yielder with extended lactation, (eg) Sindhi, Jersey Sahiwal
2. Drought breed: Bullocks are good for draught purposes, (eg) Kangeyam Malvi.
3. Dual-purpose breeds: Cows are meant for yielding more milk and bullocks are used for better drought purposes (eg) Ongole Hariana.

c) Uses of dairy product:
1. Milk: Milk is a rich source of vitamin A, B2, B and deficient in Vitamin C.
Dairy products such as yoghurt cheese butter ice cream condensed milk powder are produced from milk.
2. Meat: Meat is rich in protein and also contains minerals like iron zinc vitamins and selenium.
3. Land Management: Grazing of live stocks sometimes used as a way to control weeds.
4. Manure: Manure can be spread on agriculture fields to increase crop yields.

Question 31.
Describe the types of Chicken breeds?
Answer:
1. Egg layers: These are farmed mainly for the production of eggs.
Leghorn:

• It is originated in Italy. They are small compact with a single comb.
• They mature early and begin to lay eggs at the age of 5 or 6 months.

Chittagong:

• They are good egg layers and are delicious.
• They are found in West Bengal.

2. Selection of eggs for hatching:
Eggs should be fertile medium-sized dark brown shelled and freshly laid eggs are preferred for rearing.

3. Incubation and hatching:

• The maintenance of newly laid eggs in optimum condition till hatching is called incubation.
• The fully developed chick emerges out of egg after an incubation period of 21 – 22 days.
• There are two types of incubation namely natural incubation and artificial incubation.
• In the Natural incubation method, only a limited number of eggs can be incubated by a mother hen.
• In artificial incubation, more eggs can be incubated.

4. Brooding:

• Caring and management of young chicks for 4 – 6 weeks immediately after hatching is called brooding.
• They are natural and artificial brooding. The housing of Poultry:
• To protect the poultry from the sun.
• Rain and predators it is necessary to provide housing to poultry.
• Poultry house should be moisture-proof rat-proof and it should be easily cleanable and durable.
  5. Poultry feeding:
  The diet of chicks should contain an adequate amount of water carbohydrates proteins fats vitamins and minerals.

Poultry Products:

• The main products of poultry farmings are eggs and meat.
• The primary aim of poultry farming is to obtain eggs.

C. Poultry by-products:

• The feathers: They are used for making pillows and quilts.
• Droppings: The droppings are rich in nitrogen potash and phosphates.
• The by-products of poultry are used as good sources of nutrients for meat-producing animals and poultry.
• These by-products supply proteins fats Vitamins and minerals.
  Poultry diseases: Ranikhet coccidiosis Fowl Pox is a common poultry disease.

Merits:

1. They can adapt themselves to all types of environmental conditions.
2. And for the breed for feed efficiency.
3. Growth rate and resistance to diseases.
4. They are exhibited in poultry shows they are calm friendly and can be maintained as pets.

Question 32.
What are the types of poultry farming? What are the stages involved in rearing? What are the poultry by-products?
Answer:
Types:

1. Organic method
2. Yarding method
3. Battery cage method
4. Furnished cage method.

Stages involved in rearing:
1. Selection of the best layer.

• An active intelligent-looking bird with a bright comb not obese should be selected.
• They are golden or light yellow coloured.

2. Broiler type :

• White Plymouthrock is a fast-growing breed and soft quality meat.
• They have white plumage throughout the body. This is an American breed. It is a fast-growing breed.

3. Dual Purpose breed:
It is known for its massive body having heavy bones. Well feathered and Peacomb is one of the important breed characters.

4. Game breeds:
Aseel:

• The hens are not good egg layers but are good in the incubation of eggs.
• Aseel is noted for its pugnacity high stamina majestic gait.
• This breed is well known for its meat qualities.

5. Ornamental breeds:
Silkie:

• They are reared as pets and for egg production and meat.
• The chicken has a fluffy plumage which is said to feel like silk and satin.
• It has black skin and bones blue ear lobes and five toes on each foot.

Question 33.
Write a note on milk products?
Answer:
Milk products:
Milk is produced by dairy animals which is an emulsion of fat and lactose. Milk also contains enzymes which are destroyed during pasteurization.

Milk is a rich source of vitamin A, B„ Bp and deficient in Vitamin C. Due to its high nutrition value, it serves as a complete food for infants. Dairy products such as yoghurt, cheese, butter, ice cream, condensed milk, curd, and milk powder processed from milk make dairy, a highly farming attraction.

Tamilnadu State Board New Syllabus Samacheer Kalvi 11th Chemistry Guide Pdf Chapter 13 Hydrocarbons Text Book Back Questions and Answers, Notes.

Tamilnadu Samacheer Kalvi 11th Chemistry Solutions Chapter 13 Hydrocarbons

11th Chemistry Guide Hydrocarbons Text Book Back Questions and Answers

Textbook Evaluation:

I. Choose the best answer:

Question 1.
The correct statement regarding the comparison of staggered and eclipsed conformations of ethane, is
a) The eclipsed conformation of ethane is more stable than staggered conformation even though the eclipsed conformation has torsional strain.
b) The staggered conformation of ethane is more stable than eclipsed conformation, because staggered conformation has no torsional strain.
c) The staggered conformation of ethane is less stable than eclipsed conformation, because staggered conformation has torsional strain.
d) The staggered conformation of ethane is less stable than eclipsed conformation, because staggered conformation has no torsional strain.
Answer:
b) The staggered conformation of ethane is more stable than eclipsed conformation, because staggered conformation has no torsional strain.

Question 2.
C₂H₅ Br + 2Na C₄H₁₀ + 2NaBr.
The above reaction is an example of which of the following
a) Reimer Tiemann reaction
b) Wurtz reaction
c) Aldol condensation
d) Hoffmann reaction
Answer:
b) Wurtz reaction

Question 3.
An alkyl bromide (A) reacts with sodium in ether to form 4, 5 – diethyloctane, the compound (A) is
a) CH₃(CH₂)₃Br

b) CH₃(CH₂)₅Br

c) CH₃(CH₂)₃ CH(Br)CH₃

d)
Answer:
d)

Question 4.
The C – H bond and C – C bond in ethane are formed by which of the following types of overlap
a) sp³ – s and sp³ – sp³
b) sp² – s and sp² – sp²
c) sp – sp and sp – sp
d) p – s and p – p
Answer:
a) sp³ – s and sp³ – sp³

Question 5.
In the following reaction,

Answer:
c)

Question 6.
Which of the following is optically active
a) 2 – methyl pentane
b) citric acid
c) Glycerol
d) none of these
Answer:
a) 2 – methyl pentane

Question 7.
The compound formed at anode in the electrolysis of an aqueous solution of potassium acetate are
a) CH₄ and H₂
b) CH₄ and CO₂
c) C₂H₆ and CO₂
d) C₂H₄ and Cl₂
Answer:
c) C₂H₆ and CO₂

Question 8.
The general formula for cyclo alkanes
a) C_nH_n
b) C_nH_2n
C) C_nH_2n-2
d) C_nH_{2n + 2}
Answer:
b) C_nH_2n

Question 9.
The compound that will react most readily with gaseous bromine has the formula
a) C₃H₆
b) C₂H₂
c) C₄H₁₀
d) C₂H₄
Answer:
a) C₃H₆

Question 10.
Which of the following compounds shall not produce propene by reaction with HBr followed by elimination (or) only direct elimination reaction
a)
b) CH₃ – CH₂ – CH₂ – OH
c) H₂C = C = O
d) CH₃ – CH₂ – CH₂Br
Answer:
c) H₂C = C = O

Question 11.
Which among the following alkenes on reductive ozonolysis produces only propanone?
a) 2 – Methyl propene
b) 2 – Methyl but – 2 – ene
c) 2, 3 – Dimethyl but – 1- ene
d) 2, 3 – Dimethyl but – 2 – ene
Answer:
d) 2, 3 – Dimethyl but – 2 – ene

Question 12.
The major product formed when 2 – bromo – 2 – methyl butane is refluxed with ethanolic KOH is
a) 2 – methylbut – 2- ene
b) 2 – methyl butan – 1 – ol
c) 2 – methyl but – 1 – ene
d) 2 – methyl butan – 2- ol
Answer:
a) 2 – methylbut – 2- ene

Question 13.
Major product of the below mentioned reaction is, (CH₃)₂ C = CH₂
a) 2 – chloro – 1 – iode – 2 – methyl propane
b) 1 – chloro – 2 – iodo – 2 – methyl propane
c) 1, 2 – dichloro – 2 – methyl propane
d) 1, 2 – diiodo – 2 – methyl propane
Answer:
a) 2 – chloro – 1 – iode – 2 – methyl propane

Question 14.
The IUPAC name of the following compound is

a) trans – 2- chloro – 3- iodo – 2- pentane
b) cis – 3- iodo – 4 chloro – 3 – pentane
c) trans – 3 – iodo – 4 – chloro – 3 – pentene
d) cis – 2 – chloro – 3 iodo – 2 – pentene
Answer:
a) trans – 2- chloro – 3- iodo – 2- pentane

Question 15.
Cis – 2- butene and trans – 2 – butene are
a) conformational isomers
b) structural isomers
c) configurational isomers
d) optical isomers
Answer:
c) configurational isomers

Question 16.
Identify the compound (A) in the following reaction

Answer:
a)

Question 17.
CH ≡ CH , where A is,
a) Zn
b) conc. H₂SO₄
c) alc. KOH
d) dil. H₂SO₄
Answer:
c) alc. KOH

Question 18.
Consider the nitration of benzene using mixed con H₂SO₄ and HNO₃ if a large quantity of KHSO₄ is added to the mixture, the rate of nitration will be
a) unchanged
b) doubled
c) faster
d) slower
Answer:
d) slower

Question 19.
In which of the following molecules, all atoms are co-planar
a)

b)

c)
d) both (a) and (b)
Answer:
d) both (a) and (b)

Question 20.
Propyne on passing through red hot iron tube gives
a)

b)

c)
d) none of these
Answer:
a)

Question 21.
is

a)

b)

c) both (a) and (b)

d)
Answer:
d)

Question 22.
Which one of the following is non aromatic?
a)

b)

c)

d)
Answer:
d)

Question 23.
Which of the following compounds will not undergo Friedal – crafts reaction easily?
a) Nitro benzene
b) Toluene
c) Cumene
d) Xylene
Answer:
a) Nitro benzene

Question 24.
Some meta-directing substituents in aromatic substitution are given. Which one is most deactivating?
a) – COOH
b) – NO₂
c) -C ≡ N
d) -SO₃H
Answer:
b) – NO₂

Question 25.
Which of the following can be used as the halide component for friedal – crafts reaction?
a) Chloro benzene
b) Bromo benzene
c) Chloro ethene
d) Isopropyl chloride
Answer:
d) Isopropyl chloride

Question 26.
An alkane isobtainedbydecarboxylation of sodium propionate. Same alkane can be prepared by
a) Catalytic hydrogenation of propene
b) action of sodium metal on iodomethane
c) reduction of 1 – chloro propane
d) reduction of bromomethane
Answer:
b) action of sodium metal on iodomethane

Question 27.
Which of the following is aliphatic saturated hydrocarbon
a) C₈H₁₈
b) C₉H₁₈
c) C₈H₁₄
d) All of these
Answer:
a) C₈H₁₈

Question 28.
Identify the compound ‘Z’ in the following reaction

a) Formaldehyde
b) Acetaldehyde
c) Formic acid
d) none of these
Answer:
a) Formaldehyde

Question 29.
Peroxide effect (Kharasch effect) can be studied in case of
a) Oct – 4 – ene
b) hex – 3 – ene
c) pent – 1 – ene
d) but – 2 – ene
Answer:
c) pent – 1 – ene

Question 30.
2 – butyne on chlorination gives
a) 1 – chloro butane
b) 1, 2 – dichloro butane
c) 1, 1, 2, 2 – tetrachlorobutane
d) 2, 2, 3, 3 – tetra chloro butane
Answer:
d) 2, 2, 3, 3 – tetra chloro butane

II. Write brief answer to the following questions:

Question 31.
Give IUPAC names for the following compounds
1) CH₃ – CH = CH – CH = CH – C ≡ C – CH₃

2)

3) (CH₃)₃ C – C ≡ C – CH(CH₃)₂

4) ethyl isopropyl acetylene

5) CH ≡ C – C ≡ C – C ≡ CH
Answer:
1)

2)

3)

4) ethyl isopropyl acetylene

5)

Question 32.
Identify the compound A, B, C and D in the following series of reactions

Answer:

Question 33.
Write short notes on ortho, para directors in aromatic electrophilic substitution reactions.
Answer:
All the activating groups are ‘ortho-para’ directors.
Example: – OH, – NH₂, -NHR, -NHCOCH₃, -OCH₃ -CH₃ – C₂H₅ etc.
Let us consider the directive influences of phenolic (-OH) group. Phenol is the resonance hybrid of following structures.

In these resonance structures, the (-) charge residue is present on ortho and para position of ring structure. It is quite evident that the lone pair of electron on the atom which is attached to the ring involves in resonance and makes the ring more electron rich than benzene. The electron density at ortho and para positions increases as compared to the meta position. Therefore phenolic group activates the benzene ring for electrophilic attack at ‘ortho’ and ‘para positions and hence -OH group is an ortho-para director and activator.

In aryl halides, the strong -I effect of the halogens (electron withdrawing tendency) decreases the electron density of benzene ring, thereby deactivating for electrophilic attack. However the presence of lone pair on halogens involved in the resonance with pi electrons of benzene ring, increases electron density at ortho and para position. Hence the halogen group is an ortho-para director and deactivator.

Question 34.
How is propyne prepared from an alkene dihalide?
Answer:

Question 35.
An alkylhalide with molecular formula C₆H₁₃Br on dehydro halogenation gave two isomeric alkenes X and Y with molecular formula C₆H₁₂. On reductive ozonolysis, X and Y gave four compounds CH₃COCH₃, CH₃CHO, CH₃CH,CHO and (CH₃)₂ CHCHO. Find the alkyihalide.
Answer:

Question 36.
Describe the mechanism of Nitration of benzene.
Answer:
It is prepared by the action of a mixture of con. HNO₃ and con. H₂SO₄ (nitrating mixture) on benzene maintaining the temperature below 333 K.
Nitration:

Sulphuric acid generates the electrophile – NO₂⁺, nitronium ion-from nitric acid. This is an example of aromatic electrophilic substitution reaction.

The generation of nitronium ion
H₂SO₄ + HONO₂ → + HSO₄^–

To the nitronium ion (being an electron deficient species) the π bond of benzene, donates a pair of electrons forming a 6-bond. A species with a + ve charge is formed as an intermediate. This is called ‘arenium ion’ and is stabilised by Resonance.

In the last step, the hydrogen atom attached to the carbon carrying the nitro group is pulled out as a proton, by the Lewis base HSO₄^–, so that stable aromatic system is formed.

Question 37.
How does Huckel rule help to decide the aromatic character of a compound.
Answer:
In 1865, August Kekule suggested that benzene consists of a cyclic planar structure of six carbon with alternate single and double bonds.
There were two objections:
Benzene forms only one ortho disubstituted products whereas the Kekule’s structure predicts two o-di substituted products as shown below.

Kekule’s structure failed to explain why benzene with three double bonds did not give addition reactions like other alkenes.To overcome this objection, Kekule suggested that benzene was mixture of two forms (1 and 2) which are in rapid equilibrium.

Resonance description of benzene:
The phenomenon in which two or more structures can be written for a substance which has identical position of atoms is called resonance. The actual structure of the molecule is said to be resonance hybrid of various possible alternative structures. In benzene, Kekule’s structures I & II represented the resonance structure, and structure III is the resonance hybrid of structure I & II.
The structures 1 and 2 exist only in theory. The actual structure of benzene is the hybrid of two hypothetical resonance structures.

Spectroscopic measurements:
Spectroscopic measurements show that benzene is planar and all of its carbon- carbon bonds are of equal length 1.40 Å. This value lies between carbon-carbon single bond length 1.54 Å and carbon- carbon double bond length 1.34 Å.

Molecular orbital structure:
The structure of benzene is best de¬scribed in terms of the molecular orbital theory. All the six carbon atoms of benzene are sp² hybridized. Six sp² hybrid orbitals of carbon linearly overlap with six 1 s orbitals of hydrogen atoms to form six C – H sigma bonds. Overlap between the remaining sp² hybrid orbitals of carbon forms six C – C sigma bonds.

Formation of Sigma bond in benzene

All the σ bonds in benzene lie in one plane with bond angle 120°. Each carbon atom in benzene possess an un hybridized p-orbital containing one electron. The lateral overlap of their p-orbital produces 3 π- bond. The six electrons of the p-orbitals cover all the six carbon atoms and are said to be delocalised. Due to delocalization, strong π-bond is formed which makes the molecule stable. Hence unlike alkenes and alkynes benzene undergoes substitution reactions rather addition reactions under normal conditions.

All carbon atoms have the delocalized π MO is formed by p-orbitais the overlap of six p-orbitals.

Representation of benzene:
Hence, there are three ways in which benzene can be represented.

Question 38.
Suggest the route for the preparation of the following from benzene.
1) 3 – chloro nitrobenzene
2) 4 – chlorotoluene
3) Bromo benzene
4) m – dinitro benzene
Answer:
1) 3 – chloro nitrobenzene

2) 4 – chlorotoluene

3) Bromo benzene

4) m – dinitro benzene

Question 39.
Suggest a simple chemical test to distinguish propane and propene.
Answer:
Propene decolourises Br₂/H₂O it forms dibromo compound but propane does not react with Br₂/ H₂O.

Question 40.
What happens when Isobutylene is treated with acidified potassium permanganate?
Answer:

Question 41.
How will you convert ethyl chloride into
(i) ethane
(ii) n – butane
Answer:
(i) ethane

(ii) n – butane

Question 42.
Describe the conformers of n – butane.
Answer:
Conformations of n-Butane:
n-Butane may be considered as a derivative of ethane, as one hydrogen on each carbon is replaced by a methyl group

Eclipsed conformation:
In this conformation, the distance between the two methyl group is minimum. So there is maximum repulsion between them and it is the least stable conformer.

Anti or staggered form:
In this conformation, the distance between the two methyl groups is maximum and so there is minimum repulsion between them. And it is the most stable conformer.

The following potentially energy diagram shows the relative stabilities of various conformers of n-butane.

Question 43.
Write the chemical equations for combustion of propane.
Answer:
C₃H₈(g) + 5O₂(g) ) → 3CO₂(g) + 4H₂O(l)
propane

Question 44.
Explain Markovnikoff’s rule with suitable example.
Answer:
Markovnikoff ‘s rule:
“When an unsymmetrical alkene reacts with hydrogen halide, the hydrogen adds to the carbon that has more number of hydrogen and halogen add to the carbon having fewer hydrogen”. This rule can also be stated as in the addition reaction of alkene/alkyne, the most electro negative part of the reagent adds on to the least hydrogen attached doubly bonded carbon.

Addition of water: (Hydration of alkenes)
Normally, water does not react with alkenes. In the presence of concentrated sulphuric acid, alkenes react with water to form alcohols. This reaction follows carbocation mechanism and Markovnikoff’s rule.

Question 45.
What happens when ethylene is passed ‘ through cold dilute alkaline potassium permanganate.
Answer:
CH₂ = CH + H₂O + (O) CH₂OH – CH₂OH
Ethylene                                                                Ethylene glycol

Question 46.
Write the structures of following alkanes.
1) 2, 3 – Dimethyl – 6 – (2 – methyl propyl) decane
2) 5 – (2 – Ethyl butyl ) – 3, 3, – dimethyldecane
3) 5 – (1, 2 – Dimethyl propyl) – 2 – methylnonane
Answer:
1) 2, 3 – Dimethyl – 6 – (2 – methyl propyl) decane

2) 5 – (2 – Ethyl butyl ) – 3, 3, – dimethyldecane

3) 5 – (1, 2 – Dimethyl propyl) – 2 – methylnonane

Question 47.
How will you prepare propane from a sodium salt of fatty acid?
Answer:

Question 48.

Identify A and B
Answer:
A)

b)

Question 49.
Complete the following :

i) 2 – butyne 

ii) CH₂ = CH₂

iii)

iv) CaC₂
Answer:
i) 2 – butyne

ii) CH₂ = CH₂

iii)

iv) CaC₂
CaC₂ + 2H₂O → Ca(OH)₂ + C₂H₂↑
Calcium Carbide                  Acetylene

Question 50.
How will distinguish 1 – butyne and 2 – butyne?
Answer:

1 – butyne reacts with ammoniacal AgNO₃ solution it forms white precipitate of silver acetylide but, 2 – butyne doesnot reacts with ammoniacal AgNO₃ solution.

11th Chemistry Guide Hydrocarbons Additional Questions and Answers

I. Choose the best answer:

Question 1.
The IUPAC name of neopentane is
a) 2 – methyl butane
b) 2, 2 – dimethyl propane
c) 2 – methyl propane
d) 2, 2- dimethyl butane
Answer:
b) 2, 2 – dimethyl propane

Question 2.
Alkanes are also known as
a) olefins
b) unsaturated aliphatic hydrocarbons
c) saturated aromatic hydrocarbon
d) paraffins
Answer:
d) paraffins

Question 3.
The compressed gas available in cooking gas cylinders is a mixture of:
a) C₆H₆ + C₆H₅CH₃
b) C₂H₄ + C₂H₂
c) C₂H₄ + CH₄
d) C₄H₁₀ + C₃H₈
Answer:
d) C₄H₁₀ + C₃H₈

Question 4.
The gas supplied in cylinders for cooking is
a) marsh gas
b) LPG
c) mixture CH₄ and C₂H₆
d) mixture of ethane and propane
Answer:
d) mixture of ethane and propane

Question 5.
Adam’s catalyst is:
a) platinum metal
b) palladium
c) nickel metal
d) PtO₂
Answer:
d) PtO₂

Question 6.
Soda lime is
a) NaOH
b) NaOH + CaO
c) CaO
d) Na₂CO₃
Answer:
b) NaOH + CaO

Question 7.
Methyl bromide is converted into ethane by heating it in ether medium with
a) Al
b) Mg
c) Na
d) Cu
Answer:
c) Na

Question 8.
Hydrocarbon which is liquid at room temperature is
a) Pentane
b) Butane
c) Propane
d) Ethane
Answer:
a) Pentane

Question 9.
Pyrolysis of Methane and respectively are
a) Exothermic & Endothermic
b) Endothermic & Exothermic
c) Both are endothermic
d) Both are exothermic
Answer:
c) Both are endothermic

Question 10.
Select the correct statement about alkanes
a) they are polar in nature
b) they are soluble in water
c) they are non – combustible
d) their dipole moment is zero
Answer:
d) their dipole moment is zero

Question 11.
Final products of complete oxidation of hydrocarbon is
a) Acid
b) Dihydric alcohol
c) Aldehyde
d) H₂O + CO₂
Answer:
d) H₂O + CO₂

Question 12.
Isomerisation in alkane can be brought by using
a) Al₂O₃
b) Fe₂O₃
c) Anh.AlCl₃/ HCl at 200°C
d) Cone. H₂SO₄
Answer:
c) Anh.AlCl₃/ HCl at 200°C

Question 13.
In aromatization of n – hexane, the catalyst used is
a) Cr₂O₃
b) V₂O₅
c) Mo₂O₃
d) All
Answer:
d) All

Question 14.
The most oxidized form of ethane is
a) CO₂
b) HCHO
c) HCOOH
d) CH₃COOH
Answer:
a) CO₂

Question 15.
The following substance is used as anti knocking compound
a) TEL
b) Lead tetrachioride
c) Lead acetate
d) C₂H₂PbCl
Answer:
a) TEL

Question 16.
Conformational isomers are due to
a) Free rotation about C – C single bond
b) Frozen rotation about C – C single bond
e) Frozen rotation about C – C double bond
d) Restricted rotation about C – C single bond
Answer:
a) Free rotation about C – C single bond

Question 17.
The most stable conformation of ethane is
a) Eclipsed
b) Skew
c) Staggered
d) All are equally stable
Answer:
c) Staggered

Question 18.
IUPAC name of the following compound

a) 3 – methyl hexane
b) 3 – Ethyl pentane
c) 2, 3 – dimethyl pentane
d) 2, 2 – dimethyl pentane
Answer:
a) 3 – methyl hexane

Question 19.
The number of sigma bonds formed in ethane by the overlapping of sp3 – sp3 orbitals
a) 7
b) 5
c) 1
d) 4
Answer:
c) 1

Question 20.
How many types of carbon atoms are present in 2, 2, 3 – trimethyl pentane
a) one
b) Two
c) Three
d) Four
Answer:
d) Four

Question 21.
The correct IUPAC name of the following alkane is

a) 3, 6 – diethyl – 2- methyloctane
b) 5 – isopropyl – 3- ethyloctane
c) 3 – ethyl – 5- isopropyloctane
d) 3 – isopropyl – 6 – ethyloctane
Answer:
a) 3, 6 – diethyl – 2- methyloctane

Question 22.
In Wurtz reaction, n – hexane is obtained from
a) n – propyl chloride
b) n – butyl chloride
c) Ethyl chloride
d) isopropyl chloride
Answer:
a) n – propyl chloride

Question 23.
When sodium acetate is heated with sodalime the reaction is called
a) Dehydration
b) Decarboxylation
c) Dehydrogenation
d) Dehydrohalogenation
Answer:
b) Decarboxylation

Question 24.
The following substance reacts with water to give ethane
a) CH₄
b) C₂H₅MgBr
c) C₂H₄OH
d) C₂H₅OC₂H₅
Answer:
b) C₂H₅MgBr

Question 25.
Reaction of ROH with R’ MgX produces
a) RH
b) R’H
c) R – R
d) R’ – R”
Answer:
b) R’H

Question 26.
The solvent used in Wurtz reacton is
a) C₂H₅OH(aq)
b) CH₃COOH
c) H₂O
d) C₂H₅OC₂H₅(dry)
Answer:
d) C₂H₅OC₂H₅(dry)

Question 27.
Arrange the following in the decreasing order of their boiling points
i) n – butane
ii) 2 – methylbutane
iii) n – pentane
iv) 2 – methylbutane
a) i > ii > iii > iv
b) ii > iii > iv > i
c) iv > iii > ii > i
d) iii > ii > iv > i
Answer:
d) iii > ii > iv > i

Question 28.
The compound with the highest boiling point is
a) n – Hexane
b) n – Pentane
c) 2, 2 – dimethyl propane
d) 2 – methyl butane
Answer:
a) n – Hexane

Question 29.
The increasing order of reduction of alkyl halides with zinc and dilute HCl is
a) R – Cl < R – I < R – Br
b) R – Cl < R – Br < R – I
c) R – I < R – Br < R – Cl
d) R – Br < R – I < R – Cl
Answer:
b) R – Cl < R – Br < R – I

Question 30.
The volume of oxygen required for the complete combustion of 4 lit of ethane is
a) 4 lit
b) 8 lit
c) 12 lit
d) 14 lit
Answer:
d) 14 lit

Question 31.
The dihedral angle between the hydrogen atoms of 2 methyl groups in staggered conformation of ethane is
a) 0°
b) 60°
c) 120°
d) 240°
Answer:
b) 60°

Question 32.
The distances between the hydrogen nuclei in staggered and eclipsed form in ethane respectively are
a) 2.55 Å & 2.29 Å
b) 1.54 Å & 1.34 Å
c) 3.5 Å & 2.5 Å
d) 2.29 Å & 2.55 Å
Answer:
a) 2.55 Å & 2.29 Å

Question 33.
Energy barrier between staggered and eclipsed form in ethane is
a) 0.6 kcal / mole
b) 2.9 kcal / mole
c) 12 kcal / mole
d) 14 cal / mole
Answer:
b) 2.9 kcal / mole

Question 34.
IUPAC name of the following compound

a) 3 – Ethyl, 5 – methyl heptane
b) 5 – Ethyl, 3 – methyl heptane
c) 2 – Ethyl, 5 – methyl heptane
d) 4 – Ethyl, 5 – methyl heptane
Answer:
a) 3 – Ethyl, 5 – methyl heptane

Question 35.
Ethylene is converted to ethane in the presence of Ni at 300°C. In this reaction the hybridization of carbon changes from
a) sp to sp²
b) sp² to sp³
c) sp³ to sp
d) sp to sp³
Answer:
b) sp² to sp³

Question 36.
In which of the following reactions in the preparation of ethane a new C – C bond is formed
a) Sabatier – Senderen’s reaction
b) Reduction of ethyl iodide
c) Decarboxylation
d) Kolbe’s electrolysis
Answer:
d) Kolbe’s electrolysis

Question 37.
Select the correct statements
a) eclipsed and staggered ethanes give different products on reaction with chlorine in presence of light
b) the conformational isomers can be isolated at room temperature
c) torsional strain is minimum in ethane at dihedral angles 60°, 180° and 300°
d) steric strain is minimum in gauche form of n – butane
Answer:
c) torsional strain is minimum in ethane at dihedral angles 60°, 180° and 300°

Question 38.
The fully eclipsed conformation of n – butane is least stable due to the presence of
a) bond opposition strain only
b) steric strain only
c) bond opposition strain as well as steric strain
d) no strain is present in the molecule
Answer:
c) bond opposition strain as well as steric strain

Question 39.
Vinyl group among the following is
a) (CH₃)₂ CH –
b) HC ≡ C –
c) H₂C = CH – CH₂ –
d) CH₂ = CH –
Answer:
d) CH₂ = CH –

Question 40.
The alkene that exhibits geometrical isomerism is
a) propene
b) 2 – methyl propene
c) 2 – butene
d) 2 – methyl – 2 – butene
Answer:
c) 2 – butene

Question 41.

a) 5 – methylocta – 1, 3, 5, 7 – tetraene
b) 4 – methylocta – 1, 3, 5, 7 – tetraene
c) 4 – butenylocta -1, 3- diene
d) octa – 1, 5 – diene
Answer:
b) 4 – methylocta – 1, 3, 5, 7 – tetraene

Question 42.
CH₂ = C (CH₂CH₂CH₃)₂
a) 2 – Propyl pent – 1 – ene
b) 2 – Propyl pent – 2- ene
c) 2 – Propyl pent – 3 – ene
d) 3 – Propyl pent – 1- ene
Answer:
a) 2 – Propyl pent – 1 – ene

Question 43.
The number of sigma (σ) and pi (π) bonds in the following structure are
a) σ bonds – 33 π bonds – 2
b) σ bonds – 22 π bonds – 2
c) σ bonds – 42 π bonds – 2
d) σ bonds – 40 π bonds – 3
Answer:
a) σ bonds – 33 π bonds – 2

Question 44.
In dehydrohalogenation, hydrogen and halogen are removed from
a) the same carbon atom
b) from adjacent carbon atoms
c) from isolate carbon atoms
d) from any two carbon atoms
Answer:
b) from adjacent carbon atoms

Question 45.
Ethylene readily undergoes the following type of reaction.
a) Elimination
b) Addition
c) Rearrangement
d) Substitution
Answer:
b) Addition

Question 46.
Baeyer’s reagent is
a) Aqueous bromine solution
b) Neutral permanganate solution
c) Acidified permanganate solution
d) Alkaline potassium permanganate solution
Answer:
d) Alkaline potassium permanganate solution

Question 47.
Baeyer’s reagent oxidizes ethylene to
a) Ethylene chlorohydrin
b) Ethyl alcohol
c) CO₂ and H₂O
d) Ethane – 1, 2 – diol
Answer:
d) Ethane – 1, 2 – diol

Question 48.
On reductive ozonolysis ethylene gives
a) Aldehyde
b) Ketone
c) Carboxylic acid
d) Ether
Answer:
a) Aldehyde

Question 49.
Polythene is obtained by the polymerization of
a) Styrene
b) A mixture of ethylene and styrene
c) Acetylene
d) Ethene
Answer:
c) Acetylene

Question 50.
Polytetrafluoroethylene is commercially known as
a) Teflon
b) Freon
c) Lewisite
d) Westron
Answer:
a) Teflon

Question 51.
Polythens is
a) (- H₂C = CH₂ -)_n
b) (- HC = CH – )_n
c) (- H₃C – CH₃ – )_n
d) (- H₂C – CH₂ -)_n
Answer:
d) (- H₂C – CH₂ -)_n

Question 52.
When ethanol vapours are passed over alumina heated at 350°C, the main product obtained is
a) C₂H₆
b) C₂H₄
c) C₂H₂
d) C₂H₅OC₂H₅
Answer:
b) C₂H₄

Question 53.
Dehydrohalogenation of ethyl chloride in presence of ale. KOH produces the following
a) HC ≡ CH + KCl + H₂O
b) CH₄ + KCl + H₂O
c) CH₂ = CH₂ + KCl + H₂O
d) C₂H₄ + HCl
Answer:
c) CH₂ = CH₂ + KCl + H₂O

Question 54.
Ethylene is prepared by
a) Dehalogenation of chloroform
b) Pyrolysis of ethane at 450°C
c) Dehydration of methanol with Al₂O₃ / 350°C
d) Methyl chloride on reduction
Answer:
b) Pyrolysis of ethane at 450°C

Question 55.
The peroxide effect involves
a) Ionic mechanism
b) Free – radical mechanism
c) Heterolytic fission of double bond
d) Homolytic fission of double bond
Answer:
b) Free – radical mechanism

Question 56.
In which of the following will Kharasch effect operate?
a) CH₃ – CH₂ – CH = CH₂ + HCl
b) CH₃ – CH₂ – CH = CH₂ + HBr
c) CH₃ – CH = CH – CH₃ + HBr
d) CH₃ – CH₂ – CH = CH₂ + HI
Answer:
b) CH₃ – CH₂ – CH = CH₂ + HBr

Question 57.
Anti Markownikoff addition of HBr is not observed in
a) Propene
b) Butene – 1
c) Butene – 2
d) pentene – 2
Answer:
c) Butene – 2

Question 58.
Conditions used for the formation of ethylene glycol from ethylene
a) bromine water
b) cold alkaline KMnO₄
c) dil H₂SO₄, 60°C
d) Ag / 200°C
Answer:
b) cold alkaline KMnO₄

Question 59.
The olefin which on ozonolysis gives CH₃CH₂CHO and CH₃CHO is
a) 1 – butene
b) 2 – butene
c) 1 – pentene
d) 2 – pentene
Answer:
d) 2 – pentene

Question 60.
In the following reaction, A and B respectively are,

a) C₂H₄ and alcoholic KOH / ∆
b) C₂H₅Cl and aqueous KOH / ∆
c) C₂H₅OH and aq KOH / ∆
d) C₂H₂ and Br₂
Answer:
a) C₂H₄ and alcoholic KOH / ∆

Question 61.
The number of possible alkynes with molecular formula C₅H₈ is
a) 3
b) 4
c) 5
d) 6
Answer:
a) 3

Question 62.
The number of open chain structural isomers possible with molecular formula C5H8 is
a) 7
b) 6
c) 5
d) 4
Answer:
a) 7

Question 63.
Alkynes exhibit.
a) Chain isomerism
b) Position isomerism
c) Functional isomerism
d) All the above
Answer:
d) All the above

Question 64.
The IUPAC name of the compound having the formula CH ≡ C – CH = CH₂
a) Butene – 2 – ye
b) But – 2- yne – 3 – ene
c) 3 – butane 1 – ene
d) But – 1 – ene – 3 – yne
Answer:
d) But – 1 – ene – 3 – yne

Question 65.
Acetylene can be obtained by the electrolysis of the following compound
a) Potassium fumerate
b) Potassium succinate
c) Potassium acetate
d) Potassium formate
Answer:
a) Potassium fumerate

Question 66.
The gas obtained when ethylene chloride reacts with alcoholic potash and sodamide is
a) C₂H₄
b) C₂H₆
c) C₂H₂
d) C₂H₅Cl
Answer:
c) C₂H₂

Question 67.
PVC is the polymer of the following
a) Ethyl chloride
b) Vinyl Chloride
c) Allyl Chloride
d) Ethynyl chloride
Answer:
b) Vinyl Chloride

Question 68.
Which of the following possess acidic hydrogen
a) C₂H₆
b) C₂H₄
c) C₂H₂
d) CH₄
Answer:
c) C₂H₂

Question 69.
Hydrocarbon which gives oxyacetylene flame
a) ethane
b) ethene
c) ethyne
d) ethanol
Answer:
c) ethyne

Question 70.
The isomer of propyne
a) Allene
b) Propene
c) Cyclo propane
d) Propane
Answer:
a) Allene

Question 71.
Bond angle between C – C in alkyne
a) 109°.28′
b) 120°
c) 180°
d) 60°
Answer:
c) 180°

Question 72.
The molecule having linear structure is
a) Methane
b) Ethylene
c) Acetylene
d) Water
Answer:
c) Acetylene

Question 73.
The C – C bond length is shortest in
a) C₂H₆
b) C₃H₈
c) C₆H₆
d) C₂H₄
Answer:
b) C₃H₈

Question 74.
The hydrolysis of Mg₂C₃ produces
a) acetylene
b) propyne
c) butyne
d) ethylene
Answer:
b) propyne

Question 75.
1 – pentyne and 2 – pentyne can be distinguished by
a) Silver mirror test
b) Iodoform test
c) Addition of H₂
d) Baeyers test
Answer:
a) Silver mirror test

Question 76.
Acetylene on reaction with silver nitrate shows
a) Oxidizing property
b) Reducing property
c) Basic nature
d) Acidic nature
Answer:
d) Acidic nature

Question 77.
The acidic nature of hydrogens in acetylene cannot be explained by the reaction with
a) Sodium metal
b) Ammonical cuprous chloride solution
c) Ammonical silver nitrate solution
d) HCN
Answer:
d) HCN

Question 78.
Westron is the solvent obtained by the reaction of chlorine with
a) Ethylene
b) Ethyne
c) Ethane
d) Methane
Answer:
b) Ethyne

Question 79.
CH ≡ CH is
a) CH₂ = CH – CH = CH₂
b) HC ≡ C – CH₃
c) CH₂ = CH – CH₃
d) CH₃ – CH₂ – CH₃
Answer:
b) HC ≡ C – CH₃

Question 80.
Hydration of ethyne to ethanal takes place through the formation of
a) CH₃CH(OH)₂
b) CH₂ = CHOH
c) CH₂ = CHO^–
d) CH ≡ C^–
Answer:
b) CH₂ = CHOH

Question 81.
B is
a) Acetylene
b) Acetaldehyde
c) Acetone
d) Acetic acid
Answer:
b) Acetaldehyde

Question 82.
is
a) Ethyl chloride
b) 1, 2 dichloro ethene
c) Vinyl chloride
d) Ethylidine chloride
Answer:
c) Vinyl chloride

Question 83.
The Polymer ‘B’ is
a) orlon
b) PVC
c) nylon
d) Teflon
Answer:
b) PVC

Question 84.
Benzene is ______ molecule.
a) Tetrahedral
b) Planar
c) Trigonal
d) Square planar
Answer:
b) Planar

Question 85.
Bond length of C – C in benzene.
a) 1.34 Å
b) 1.39 Å
c) 1.54 Å
d) 1.20 Å
Answer:
c) 1.54 Å

Question 86.
The resonance energy Benzene is
a) 36 kcal / mol
b) 85.8 kJ / mole
c) 150.48 kJ / mole
d) Both (a) and (c)
Answer:
d) Both (a) and (c)

Question 87.
In Huckel’s (4n + 2) π rule for aromaticity, ‘n’ represents
a) Number of carbon atoms
b) Number of rings
c) Whole number
d) Fractional number (or) integer (or) zero
Answer:
c) Whole number

Question 88.
Coal tar is obtained as a by product during
a) Destructive distillation of wood
b) Destructive distillation of coal
c) Destructive distillation of bones
d) steam distillation of light oil
Answer:
b) Destructive distillation of coal

Question 89.
Gammaxene is ________ isomer of benzene hexa chloride.
a) α
b) β
c) γ
d) δ
Answer:
c) γ

Question 90.
The empirical formula of benzene and acetylene is/are
a) CH₂, CH
b) CH₂, CH₂
c) CH, CH
d) CH₃, CH₃
Answer:
c) CH, CH

Question 91.
Chemical name of the insecticide gammaxene is
a) DDT
b) Benzene hexa chloride
c) Chloral
d) Hexa chloro ethane
Answer:
b) Benzene hexa chloride

Question 92.
Which is non benzenoidal aromatic compound?
a) Benzene
b) Pyridine
c) Toluene
d) Phenol
Answer:
b) Pyridine

Question 93.
Benzene is purified by
a) distillation
b) fractional distillation
c) Evaporation
d) sublimation
Answer:
b) fractional distillation

Question 94.
Preparation of benzene from phenol is
a) Reduction
b) Oxidation
c) Addition
d) Dehydrogenation
Answer:
a) Reduction

Question 95.
The true statement about benzene is
a) Because of unsaturation benzene easily undergoes addition reactions
b) There are two types C – C bonds in benzene molecule
c) There is a cyclic delocalization of pi – electrons in benzene
d) Mono substitution of benzene gives three isomeric products
Answer:
c) There is a cyclic delocalization of pi – electrons in benzene

Question 96.
– COOH group in electrophilic substitution directs the incoming group to
a) o – position
b) p – position
c) m – position
d) o – and p – position
Answer:
c) m – position

Question 97.
Which of the following is not meta directing group?
a) -SO₃H
b) – NO₂
c) – CN
d) – NH₂
Answer:
d) – NH₂

Question 98.
Which among the following is very strong o – , p – directing group?
a) – Cl
b) – OR
c) – NH₂
d) – NHR
Answer:
d) – NHR

Question 99.
Cyclo butadiene is said to be
a) Aromatic
b) Aliphatic
c) anti aromatic
d) heterocyclic
Answer:
c) anti aromatic

Question 100.
In the reaction
the attacking species is
a) Cl₂
b) Cl⁺
c) Cl^–
d) FeCl₄^–
Answer:
b) Cl⁺

Question 101.
The electrophile in Acetylation of Benzene

Answer:
b)

Question 102.
The ratio of sigma and pi bonds in benzene is
a) 4 : 1
b) 2 : 3
c) 6 : 1
d) 1 : 1
Answer:
a) 4 : 1

Question 103.
Benzene reacts with _______ to yield acetophenone.
a) CH₃COCl + AlCl₃
b) C₆H₅COCl + AlCl₃
c) RCOCl + AlCl₃
d) C₂H₅COCl + AlCl₃
Answer:
a) CH₃COCl + AlCl₃

Question 104.
The order of activites of the various O and P director is
a) – O^– > – OH > – OCOCH₃ > – COCH₃
b) – OH > – O^– > – OCOCH₃ > – COCH₃
c) – OH > – O^– > – COCH₃ > – OCOCH₃
d) -O^– > – COCH₃ > -OCOCH₃ > -OH
Answer:
a) – O^– > – OH > – OCOCH₃ > – COCH₃

II. Very short question and answers (2 Marks):

Question 1.
What are alkanes? Give example.
Answer:
Alkanes are saturated hydrocarbons represented by the general formula C_nH_{2n + 2} where ‘n’ is the number of carbon atoms in the molecule. Methane CH₄, is- the first member of alkane family. The successive members are ethane C₂H₆, propane C₃H₈,butane C₄H₁₀, pentane C₅H₁₂ and so on. It is evident that each member differs from its proceeding or succeeding member by a -CH₂ group.

Question 2.
Give the IUPAC name of the following alkane.
a)

b)
Answer:
a)

b)

Question 3.
Draw the structural formula for 4,5 – diethyl – 3, 4, 5 – trimethyl octane.
Answer:

Question 4.
How is methane prepared from sodium acetate?
Answer:
When a mixture of sodium salt of carboxylic acid and soda lime (sodium hydroxide + calcium oxide) is heated, alkane is formed. The alkane formed has one carbon atom less than carboxylic acid. This process of eliminating carboxylic
group is known as decarboxylation.
CH₃COONa + NaOH CH₄ + Na₂CO₃
Sodium acetate                            Methane

Question 5.
Write a short note on Kolbe’s Electrolytic method.
Answer:
When sodium or potassium salt of carboxylic acid is electrolyzed, a higher alkane is formed. The decarboxylative dimerization of two carboxylic acid occurs. This method is suitable for preparing symmetrical alkanes(R-R).

Question 6.
How will you convert chloro propane into propane?
Answer:
When chloro propane is reduced with Zn / HCl it gives propane.
Example:

Question 7.
Explain the combustion reaction of alkane with suitable example.
Answer:
A combustion reaction is a chemical reaction between a substances and oxygen with evolution of heat and light (usually as a flame). In the presence of sufficient oxygen, alkanes undergoes combustion when ignited and produces carbondioxide and water.

The combustion reaction is expressed as follows.
Example:
CH₄ + 2O₂ → CO₂ + 2H₂O
∆H° = -890.4 KJ

When alkanes burn in insufficient supply of oxygen, they form carbonmonoxide and carbon black.
2CH₄ + 3O₂ 2CO + 4H₂O
CH₄ + O₂ → C + 2H₂O

Question 8.
How are the following compound prepared by Aromatisation method?
(i) Benzene
(ii) Toluene
Answer:
(i) Benzene
n-Hexane passed over Cr₂O₃ supported on alumina at 873 k gives benzene.

(ii) Toluene

Question 9.
What happens when methane reacts with steam?
Answer:
Methane reacts with steam at 1273K in the presence of Nickel and decomposes to form carbon monoxide and hydrogen gas.
CH₄(g) + H₂O(g) CO(g) + 3H₂
Production of H₂ gas from methane is known as steam reforming process and it is a well-established industrial process for the production of H₂ gas from hydrocarbons.

Question 10.
Explain the Isomerisation reaction with suitable example.
Answer:
Isomerisation is a chemical process by which a compound is transformed into any its isomeric forms. Normal alkanes can be converted into branched alkanes in the presence of AlCl₃ and HCl at 298 k.

This process is of great industrial importance. The quality of gasoline is improved by isomerising its components.

Question 11.
What are alkenes? Give example.
Answer:
Alkenes are unsaturated hydrocarbons that contain carbon-carbon double bond. They are represented by the general formulae C_nH_2n where ‘n’ stands for number of carbon atoms in the molecule. Alkenes are also known as olefins (in Latin – oil maker) because the first member ethene combines with chlorine gas to form an oily liquid as a product.
Example:
Ethylene (C₂H₄)

Question 12.
Explain the Geometrical isomerism of alkene with suitable example.
Answer:
It is a type of stereoisomerism and it is also called cis-trans isomerism. Such type of isomerism results due to the restricted rotation of doubly bounded carbon atoms.
If the similar groups lie on the same side, then the geometrical isomers are called Cis-isomers. When the similar groups lie on the opposite side, it is called a Trans isomer.
Example:
The geometrical isomers of 2-Butene is expressed as follows

Question 13.
Write the test for Alkene.
Answer:
Bromine in water is reddish brown colour. When small about of bromine water is added to an alkene, the solution is decolourised as it forms dibromo compound. So, this is the characteristic test for unsaturated compounds.
Example:

Question 14.
Mention uses of Alkenes.
Answer:

• Alkenes find many diverse applications in industry. They are used as starting materials in the synthesis of alcohols, plastics, liquors, detergents and fuels
• Ethene is the most important organic feed stock in the polymer industry. E.g,’ PVC, Sarans and polyethylene. These polymer are used in the manufacture of floor tiles, shoe soles, synthetic fibres,raincoats, pipes etc.

Question 15.
How is propyne prepared from propylidine chloride?
Answer:

Question 16.
How is ethyne prepared from CaC₂?
Answer:
Ethyne can be manufactured in large scale
by action of calcium carbide with water.

Calcium carbide needed for this reaction is prepared by heating quick lime and coke in an electric furance at 3273 K
CaO + 3C CaC₂ + CO

Question 17.
Write the reaction of propyne using Br₂.
Answer:

When Br₂ in CCl₄ (Reddishbrown) is added to an aikyne, the colour is decolounsed. This is the test for unsaturation.

Question 18.
Mention the uses of alkynes.
Answer:

1. Acetylene is used in oxy acetylene torch used for welding and cutting metals.
2. It is used for manufacture of PVC, polyvinyl acetate, polyvinyl ether, orlon and neoprene rubbers.

III. Short question and answers (3 Marks):

Question 1.
How are the following conversions carried out?
(i) propene → propane
(ii) ethene → ethane
(iii) prop – 1 – yne → propane
Answer:
(i) propene → propane
CH₃ – CH = CH₂ + H₂ CH₃ – CH₂ – CH₃
propene                                     propane

(ii) ethene → ethane
CH₂ = CH₂ + H₂ CH₃ – CH₃
ethene                               ethane

(iii) prop – 1 – yne → propane
CH₃ – C ≡ CH + 2H₂ CH₃ – CH₂ – CH₃
prop – 1 – yne                            propane

Question 2.
write the IUPAC name of the following compounds.

Answer:

Question 3.
Write the structural formula for the following compounds.
(i) 3 – Ethyl – 4, 5 – dipropyl octane
(ii) 2, 3 – Dimethyl pentane
(iii) 4 – Ethyl – 2,7 – Dimethyl octane
Answer:
(i) 3 – Ethyl – 4, 5 – dipropyl octane

(ii) 2, 3 – Dimethyl pentane

(iii) 4 – Ethyl – 2,7 – Dimethyl octane

Question 4.
Write a short note on
(i) Wurtz reaction
(ii) Corey – House Mechanism
Answer:
(i) Wurtz reaction:
When a solution of halo alkanes in dry ether is treated with sodium metal, higher alkanes are produced. This reaction is used to prepare higher alkanes with even number of carbon atoms.
Example:
CH₃ – Br + 2Na + Br – CH₃ CH₃ – CH₃ + NaBr
methyl bromide                                        ethane

(ii)Corey-House Mechanism:
An alkyl halide and lithium di alkyl cuprate are reacted to give higher alkane.
Example:
CH₃CH₂Br + (CH₃)₂LiCu → CH₃CH₂CH₃ + CH₃Cu + LiBr
Ethyl bromide

Question 5.
How is methane prepared from Grignard reagent?
Answer:
Methyl chloride reacts with magnesium in presence of dry ether gives methyl magnesium chloride. Then methyl magnesium chloride reacts with water to give methane.
CH₃ – Cl + Mg CH₃MgCl
chloromethane                 methyl magnesium chloride

CH₃MgCl + H₂O → CH₄ + Mg(OH)Cl
methane

Question 6.
What is meant by pyrolysis? Explain the pyrolysis reaction of Ethane and propane.
Answer:
Pyrolysis is defined as the thermal decomposition of organic compound into smaller fragments in the absence of air through the application of heat. ‘Pyro’ means ‘fire’ and ‘lysis’ means ‘separating’. Pyrolysis of alkanes also named as cracking.

In the absence of air, when alkane vapours are passed through red-hot metal it breaks down into simpler hydrocarbons.

1)

2) 2CH₃ – CH₃   CH₂ = CH₂ + 2CH₄
Ethane                                 Ethylene

Question 7.
Mention the uses of alkanes.
Answer:
The exothermic nature of alkane combustion reaction explains the extensive use of alkanes as fuels. Methane present in natural gas is used in home heating. Mixture of propane and butane are known as LPG gas which is used for domestic cooking purpose. GASOLINE is a complex mixture of many hydrocarbons used as a fuel for internal combustion engines.

Carbon black is used in the manufacture of ink, printer ink and black pigments. It is also used s fillers.

Question 8.
Write all possible structural isomers with the molecular formula C₄H₁₀ and name them.
Answer:
(i) CH₃ – CH = CH – CH₃ 2 – butene
(ii) CH₂ = CH – CH₂ – CH₃ 1 – butene
(iii) 2 – mehyl – 1 – propene
structures (i) 8s (ii) are position isomers, structures (i) & (iii), (ii) 8s (iii) are chain isomers.

Question 9.
How is ethene prepared by Kolbe’s electrolytic method?
Answer:
When an aqueous solution of potassium succinate is electrolyzed between two platinum electrodes, ethene is produced at the anode.

Question 10.
How are the following compounds prepared by ozonolysis method?
(i) Formaldehyde
(ii) Acetaldehyde
Answer:
(i) Formaldehyde:

(ii) Acetaldehyde:

Question 11.
How ozone reacts with 2 – methyl propene?
Answer:

When 2 – methyl propene reacts with ozone to give ozonoid. Ozonide is treated with Zn/H₂O gives acetone.

Question 12.
How is acetylene prepared from ethylene?
Answer:
This process involves two steps:
(i) Halogenation of alkenes to form vicinal dihalides
(ii) Dehalogenation of vicinal dihalides to form alkynes.

Question 13.
How is acetylene prepared by Kolbe’s electrolytic method?
Answer:
Electrolysis of sodium or potassium salt of maleic or fumaric acid yields alkynes.

Question 14.
Write Ozonolysis reaction of Propyne?
Answer:

Question 15.
How is BHC prepared? Give its uses.
Answer:
Chlorination of Benzene:
Benzene reacts with three molecules of Cl₂ in the presence of sun light or UV light to yield Benzene Hexa Chloride (BHC) C₆H₆Cl₆. This is known as gammaxane or Lindane which is a powerful insecticide.

Question 16.
How propane is prepared form 1, 2 – dichloro propane?
Answer:

Question 17.
Explain the polymerization reaction of alkenes.
Answer:
A polymer is a large molecule formed by the combination of larger number of small molecules. The process is known as polymensation. Alkenes undergo polymerisation at high temperature and pressure, in the presence of a catalyst.
Example:
red hot

Question 18.
Write a note on acidic nature of Alkynes.
Answer:
An alkyne shows acidic nature only if it contains terminal hydrogen. This can be explained by considering sp hybrid orbitals of carbon atom in alkynes. The percentage of S-character of sp hybrid orbital (50%) is more than sp² hybrid orbital of alkene (33%) and sp³ hybrid orbital of alkane (25%). Because of this, Carbon becomes more electronegative facilitating donation of H+ ions to bases. So hydrogen attached to triply bonded carbon atoms is acidic but not the others.

Question 19.
Write a short note on
(i) Wurtz – Fittig reactions
(ii) Friedel Craft’s reaction
Answer:
(i) Wurtz – Fittig reactions:
When a solution of bromo benzene and iodo methane in dry ether is treated with metallic sodium, toluene is formed.

(ii) Friedel Craft’s reaction:
When benzene is treated with methyl chloride in the presence of anhydrous aluminium chloride, toluene is formed.

IV. Long Question and answers (5 Marks):

Question 1.
How to draw structural formula for given IUPAC name with suitable example.
Answer:
After you learn the rules for naming alkanes, it is relatively easy to reverse the procedure and translate the name of an alkane into a structural formula. The example below show how this is done.
Let us draw the structural formula for
3 – ethyl – 2, 3 – dimethyl pentane
Step 1:
The parent hydrocarbon is pentane. Draw the chain of five carbon atoms and number it. .

Step 2:
Complete the carbon skeleton by attaching the alkyl group as they are specified in the name. An ethyl group is attached to carbon 3 and two methyl groups are attached to carbon 2 and 3.

Step 3:
Add hydrogen atoms to the carbon skeleton so that each carbon atoms has four bonds.

Question 2.
Explain the conformations of ethane.
Answer:
The two tetrahedral methyl groups can rotate about the carbon – carbon bond axis yielding several arrangements called conformers. The extreme conformations are staggered and eclipsed conformation. There can be number of other arrangements between staggered and eclipsed forms and their arrangements are known as skew forms.
Eclipsed conformation:

In this conformation, the hydrogen’s of one carbon are directly behind those of the other. The repulsion between the atoms is maximum and it is the least stable conformer.

Staggered conformation:

In this conformation, the hydrogen’s of both the carbon atoms are far apart from each other. The repulsion between the atoms is minimum and it is the most stable conformation.

Skew conformation:

The infinite numbers of possible intermediate conformations between the two extreme conformations are referred as skew conformations. The stabilities of various conformations of ethane are:
Staggered > Skew > Eclipsed
The potential energy difference between the staggered and eclipsed conformation of ethane is around 12.5 kJmol^-1. The various conformations can be represented by new man projection formula.

Eclipsed Skew Staggered newmann projection formula for Ethane.

Question 3.
Explain the steps involved in the mechanism of halogenations of alkane.
Halogenation:
A Halogenation reaction is the chemical reaction between an alkane and halogen in which one or more hydrogen atoms are substituted by the halogens.

Chlorination and Bromination are two widely used halogenation reactions. Fluorination is too quick and iodination too slow. Methane reacts with chlorine in the presence of light or when heated as follows.

Mechanism:
The reaction proceeds through the free radical chain mechanism. This mechanism is characterized by three steps initiation, propagation and termination.

(i) Chain Initiation:
The chain is initiated by UV light leading to homolytic fission of chlorine molecules into free radicals (chlorine atoms).

Here we choose Cl – Cl bond for fission because C – C & C – H bonds are stronger than Cl – Cl.

ii) Propagation:
It proceeds as follows
a) Chlorine free radial attacks the methane molecule and breaks the C – H bond resulting in the generation of methyl free radical

b) The methyl free radical thus obtained attacks the second molecule of chlorine to give chloromethane (CH₃Cl) and a chlorine free radical as follows.

c) This chlorine free radical then cycles back to step a) and both step a) and b) are repeated many times and thus chain of reaction is set up.

iii) Chain termination:
After sometimes, the reactions stops due to consumption of reactant and the chain is terminated by the combination of free radicals.

Question 4.
Write the IUPAC name of the following compounds.
1) CH₃ – CH = CH₂
2) CH₃ – CH = CH – CH₃
3)
4)
Answer:

Question 5.
Write the IUPAC name of the following compounds.

Answer:
1)

2)

3)

4)

Question 6.
Draw the structures for the following alkenes.
(i) 6 – Bromo – 2, 3 – dimethyl – 2 – hexene
(ii) 5 – Bromo – 4 – chloro – 1 -heptene
(iii) 2, 5 – dimethyl – 4 – octene
(iv) 4 – Methyl – 2 – pentene
Answer:
(i) 6- Bromo – 2, 3-dimethyl – 2 -hexene

(ii) 5 – Bromo – 4 – chloro – 1 -heptene

(iii) 2, 5 – dimethyl – 4 – octene

(iv) 4 – Methyl – 2 – pentene

Question 7.
Draw the structure and write down the IUPAC name for the isomerism exhibited by the molecular formulae:
(i) C₅H₁₂ – Pentene (3 isomers)
(ii) C₆H₁₄ – Hexene (5 isomers)
(iii) C₅H₁₂ – Pentene (3 isomers)
Answer:
(i) C₅H₁₂ – Pentene
a) CH₃ – CH₂ – CH₂ – CH = CH₂
1 – Pentene

b)
2 – methyl – 2 – butene

c) CH₃CH = CH – CH₂CH₃
2 – pentene

(ii) C₆H₁₄ – Hexene
a) CH₃ – CH₂ – CH₂ – CH₂ – CH = CH₂
1 – hexane

b) CH₃ – CH₂ – CH₂ – CH = CH – CH₃
2 – hexane

c) CH₃ – CH₂ – CH = CH – CH₃ – CH₂
3 – hexane

d)

e)

Question 8.
How are the following conversions carried out?
(i) ethanol → ethene
(ii) 2- butyne cis → 2 – butene and trans – 2 – butane
(iii) 1 – bromopropane → prop – 1 – ene
(iv) 1 – 2 – dibromoethane – ethene
Answer:
1) ethanol → ethene
C₂H₅OH H₂C = H₂C
ethanol ethane

(ii) 2 – butyne → cis – 2 – butene
H₃C – C ≡ C – CH₃ + H₂

2 – butane → trans – 2 – butane

(iii) 1 – bromopropane → prop – 1 – ene
H₃C – CH₂ – CH₂ – Br H₃C – CH = CH₂ + KBr + H₂O
1 – bromopropane → prop – 1 – ene

(iv) 1 – 2 – dibromoethane – ethene

1 – 2 – dibromoethane – ethene

Question 9.
Write the mechanism involved in the addition of HBr to alkene in the presence of organic peroxide.
Answer:
Anti-Markovnikoff’s Rule (Or) Peroxide Effect (Or) KharaschAddition:
The addition of HBr to an alkene in the presence of organic peroxide takes place in the direction opposite to that predicted by Markovnikoff’s rule.
CH₃ – CH = CH₂ + HBr CH₃ – CH₂ – CH₃ – CH₂ – CH₂ – Br
prop – 1 – ene                                                          1 – bromopropane

Mechanism:
The reaction proceeds via free radical mechanism.

Step 1:
The week O – O single bond linkages of peroxides undergoes homolytic cleavage to generate free radical.

Step 2:
The radicals abstract H from HBr thus generating bromine radical.

Step 3:
The Bromine radical adds to the double bond in the way to form more stable alkyl free radical.

Step 4:
Addition of HBr to secondary free radical

Step 5:
Addition of HBr to primary free radical

Question 10.
How are the following conversions carried out?
Answer:
(i) Propene → 2 – Propanol
(ii) ethene → ethylene glycol
(iii) 2 – butene → Acetic acid
(iv) 2 – methyl – 1 – propene → Acetone
Answer:
(i) Propene → 2 – Propanol

(ii) ethene → ethylene glycol

(iii) 2 – butene → Acetic acid

(iv) 2 – methyl – 1 – propene → Acetone

Question 11.
An organic compound (A) C₂H₄ decolourises bromine water. (A) on reaction with chlorine gives (B) A reacts with HBr to give (C). Identity (A), (B), (C). Explain th. reactions.
Answer:

Result:
(A) – ethylene
(B) – 1, 2 – dichloroethane
(C) – ethyl bromide

Question 12.
How are the following conversions carried out?
(i) 2 – butyne → 2, 2 – dichlorobutane
(ii) 1 – butyne → 2, 2 – dibromobutane
(iii) ethyne → acetaldehyde
(iv) Propyne → propan – 2 – one
Answer:
(i) 2 – butyne → 2, 2 – dichlorobutane

(ii) 1 – butyne → 2, 2 – dibromobutane

(iii) ethyne → acetaldehyde

(iv) Propyne → propan – 2 – one

Question 13.
How are the following compounds prepared from ethyne?
(i) Formic acid
(ii) Vinyl ethylene
(iii) Benzene
Answer:
(i) Formic acid

(ii) Vinyl ethylene
2CH ≡ CH CH₂ = CH – C ≡ CH (Vinyl ethylene)

(iii) Benzene

Question 14.
Explain the Huckel’s rule of Aromaticity.
Answer:
Huckel proposed that aromaticity is a function of electronic structure. A compound may be aromatic, if it obeys the following rules (Huckel’s rule)
i) The molecule must be co-planar
ii) Complete delocalization of n electron in the ring
iii) Presence of (4n+2) n electrons in the ring where n is an integer (n = 0,1,2….)
This is known as Huckle’s rule.
Some of the examples which obey Huckel rule.

1. The benzene ring is planar with delocalized π electrons (6)
It obeys Huckel’s rule because 4n + 2 = (4 × 1) + 2 = 6π electrons.
Hence, it is an aromatic compound

2. It has planar ring structure with delocalized π electrons (10).
Applying Huckle’s rule (4 × 2) + 2 = 10π electrons.
Hence it is an aromatic compound

Naphthalene

3. It has a planar ring structure with delocalized π electrons(14).
Applying Huckle’s rule (4 × 3) + 2 = 14π electrons.

4. It has planar ring structure but the π electrons are not delocalized.
Applying Huckle’s rule (4 × 1) + 2 = 6π electrons.
But it has only 4electrons. So it is not an aromatic compound

5. It has a tub shaped ring structure. It does not obey Huckel’s rule.
Applying Huckle’s rule 4n + 2 = 8π electrons if n = 2
So it is not an aromatic compound.

Question 15.
Explain the Kekule’s structure of benzene.
Answer:
In 1865, August Kekule suggested that benzene consists of a cyclic planar structure of six carbon with alternate single and double bonds.
There were two objections:
(i) Benzene forms only one orthodisubstituted products whereas the Kekule’s structure predicts two o-di substituted products as shown below.

Presence of double bond between the substituents

Presence of single bond between the substituents

(ii) Kekule’s structure failed to explain why benzene with three double bonds did not give addition reactions like other alkenes.To overcome this objection, Kekule suggested that benzene was mixture of two forms (1 and 2) in rapid equilibrium.

Question 16.
Explain the resonance in benzene.
Answer:
The phenomenon in which two or more structures can be written for a substance which has identical portions of atoms in called resonance. The actual structure of the molecule is said to be resonance hybrid of various possible alter nature structures. In benzene, Kekule’s structures I & II represented the resonance structure, and structure III is the resonance hybrid of structure I & II.

The structures 1 and 2 exist only in theory. The actual structure of benzene is the hybrid of two hypothetical resonance structures.

Question 17.
Write the industrial preparation of benzene from coal tar.
Answer:
Coal tar is a viscous liquid obtained by the pyrolysis of coal. During fractional distillation, coal tar is heated and distills away its volatile compounds namely benzene, toluene, xylene in the temperature range of 350 to 443 K. These vapours are collected at the upper part of the fractionating column

Question 18.
How is benzene prepared from
(i) Acetylene
(ii) Decarboxylation
(iii) Phenol
Answer:
(i) From acetylene
Acetylene on passing through a red -hot tube trimerises to give benzene. We havealready studied this concept in polymerization of alkynes.

(ii) Decarboxylation of aromatic acid.
When sodium benzonate is heated with sodalime, benzene vapours distil over.
C₆H₅COONa + NaOH C₆H₆ + Na₂CO₃

(iii) Preparation of benzene from Phenol
When phenol vapours are passed over zinc dust, then it is reduced to benzene.
C₆H₆OH + Zn  C₆H₆ + ZnO

Question 19.
Explain Electrophilic substitution reaction of benzene.
Answer:
(i) nitration:
When benzene is heated at 330K with a nitrating mixture (Con. HNO₃ + Con. H₂SO₄), nitro benzene is formed by replacing of hydrogen atom by nitronium ion NO₂⁺ (electrophile).

Concentrated H₂SO₄ is added to produce nitronium ion NO₂⁺.

(ii) Halogenation:
Benzene reacts with halogens (X₂ = Cl₂, Br₂,) in the presence of Lewis acid such as FeCl₃, FeBr₃ orAlCl₃ and give corresponding halo benzene.

(iii) Sulphonation:
Benzene reacts with fuming sulphuric acid (Con. H₂SO₄ + SO₃) and gives benzene sulphonic acid. The electrophile SO₃ is a molecule.

(iv) Friedel craft’s alkylation: (methylation)
When benzene is treated with a alkyl halide in the presence of only AlCl₃, alkyl benzene is formed.

(v) Friedel craft’s acylatlon: (Acetylation)
When benzene is treated with acetyichioride in the presence of AlCl₃, acyl benzene is formed.

Question 20.
How is benzene converted into
a) Cyclo hezane
b) maleic anhydride
c) 1, 4 cyclo hexadiene
Answer:
a) Cyclo hexane:
Benzene reacts with hydrogen in the presence of Platinum or Palladium to yield Cyclohexane. This is known as hydrogenation.

b) maleic anhydride:
Although benzene is very stable to strong oxidizing agents, it quickly undergoes vapour phase oxidation by passing its vapour mixed with oxygen over V₂O₅ at 773k. The ring breaks to give maleic anhydride.

c) 1, 4 cyclo hexadiene:
Benzene can be reduced to non- conjugated dienes 1, 4 – cyclohexadiene by treatment with Na or Li in a mixture of liquid ammonia and alcohol. It is the convenient method to prepare cyclicdienes.