Chapter-8 Atmospheric Pollution Class-9 Concise Chemistry

Revised Selina Publishers Chemistry Solutions ICSE Class 9

Chapter-8 Atmospheric Pollution Class-9 Concise Selina Chemistry Solutions. Step by Step Solutions of Chapter-8 Atmospheric Pollution Class-9 with Exercise-8(A), Exercise-8(B), Exercise-8(C),Exercise-8(D). Solutions of Revised Concise Chemistry Selina Publishers Chapter-8 Atmospheric Pollution Class-9. This post is the Solutions of Revised Concise Selina Chemistry for ICSE Class 9 Chapter-8 Atmospheric Pollution Class-9

Chapter-8 Atmospheric Pollution Class-9 Concise Chemistry Solutions

Note :-  Before Viewing Revised Concise Selina Solutions of Chapter-8 Atmospheric Pollution Class-9 . Read the whole chapter carefully . focus on Air Pollution, Acid rain, Global warming and Ozone.

-: Select topics:-

Air Pollution Exercise-8(A) ,

Acid Rain Exercise-8(B) ,

Global Warming Exercise-8(C)

Ozone Exercise-8(D) ,

Exercise-8(A) Selina Solutions of Chapter-8 Atmospheric Pollution Chemistry for ICSE Class-9 

Question 1

Define the following terms:

(i) pollution

(ii) pollutant

(iii) air pollution

Answer 1

(i) Pollution :- Pollution may be defined as contamination of air, water or soil by      undesirable amounts of materials or heat and is caused by the  concentration of substances which have harmful effects.

(ii) Pollutant :- Toxic and otherwise harmful substances which have an undesirable  impact on different components of the environment and life forms are    known as pollutants.

(iii) air pollution :- Air pollution means degradation of air quality due to concentration  of harmful contaminants which affect human, plant and animal lives.

Question 2

Name any four gaseous pollutants.

Answer 2

Sulphur dioxide, hydrogen sulphide, carbon monoxide and hydrocarbons.

Question 3

Name the compounds of sulphur that cause air pollution. Also state the harmful effects of sulphur compounds.

Answer 3

Compounds of sulphur like sulphur dioxide, sulphur trioxide and hydrogen sulphide are pollutants.

Harmful effects of oxides of sulphur:

(a) It causes headache, vomiting and even death due to respiratory failure.

(b)and  It destroys vegetation and weakens building materials/constructions.

(c)mixes with smoke and fog to form smog, which is very harmful.

It is oxidised by atmospheric oxygen into sulphur trioxide (SO3) which combines with water to form sulphuric acid.

2SO2(g) + O2(g) →2SO3(g)
SO3(g) + H2O(l) → H2SO4(l)

 

Question 4

State:

(i) natural sources of air pollution

(ii) man-made sources of air pollution

Answer 4

(i) natural sources of air pollution are:-Volcanoes, decaying vegetation, forest fires and dust storms

(ii) man-made sources of air pollution:-Automobiles, factories, industrial processes and decay of crop  residue in rural areas

Question 5

(a) How do oxides of nitrogen enter the atmosphere?

(b) What are their harmful effects?

Answer 5 

 (a)  oxides of nitrogen enter the atmosphere

  • Oxides of nitrogen, nitric oxide (NO) and nitrogen dioxide (NO2), enter the atmosphere in the following ways:
  • On burning of fuels in furnaces, the temperature increases. At high temperature, nitrogen and oxygen present in the air combine to form oxides of nitrogen.
  • Oxides of nitrogen are produced during the burning of fuel in an internal combustion engine. They enter the atmosphere as exhaust gases.
  • During thunderstorms, nitric oxide is formed by the reaction between atmospheric nitrogen and oxygen in the presence of electric discharge.
  • Nitric oxide further reacts with atmospheric oxygen and ozone to form nitrogen dioxide.

(b) Harmful effects of the oxide of nitrogen:


Nitrogen dioxide is very harmful to plants and animals.

  • It causes irritation in the mucous membrane.
  • Large concentrations of NO2 may cause serious lung diseases.
  • Nitrogen dioxide causes serious injury to vegetation; it damages plant leaves.
  • In sunlight, nitrogen dioxide oxidises hydrocarbons to form photochemical smog. Photochemical smog causes eye irritation, asthma attacks and nasal and throat infections.

Question 6

State the origin and health impact of smog.

Answer 6

Smog is a dark, thick, dust and soot-laden fog pollutant which is a combination of oxides of nitrogen and sulphur and of partially oxidisedhydrocarbons and their derivatives produced by industries and automobiles.

Smog is noxious and irritating. It reduces visibility, induces respiratory troubles and can cause death by suffocation.

Question 7

What are the harmful effects of oxides of sulphur?

Answer 7

Harmful effects of oxides of sulphur:

(a) It causes headache, vomiting and even death due to respiratory failure.

(b) It destroys vegetation and weakens building materials/constructions.

(c) It mixes with smoke and fog to form smog, which is very harmful.

It is oxidised by atmospheric oxygen into sulphur trioxide (SO3) which combines with water to form sulphuric acid.

2SO2(g) + O2(g) →2SO3(g)
SO3(g) + H2O(l) → H2SO4(l)

Question 8

State the main sources and effects of carbon monoxide.

Answer 8

Carbon monoxide is formed by incomplete combustion of fuels in homes, factories and automobiles.

Effects of carbon monoxide are as follows:

  • It is a highly poisonous gas.
  • It reduces the oxygen-carrying capacity of blood by an amount equivalent to the amount of haemoglobin converted to carboxyhaemoglobin.
    Haemoglobin + CO → Carboxyhaemoglobin
  • Because heart and brain are the two tissues most sensitive to oxygen depletion, they show the most serious effects of carbon monoxide exposure.
    In high concentrations, carbon monoxide may kill by paralysing normal brain action.

Question 9

Give the mechanism of the action of carbon monoxide.

Answer 9

It is a highly poisonous gas.

When inhaled, it passes through the lungs directly into the blood stream. There it combines with haemoglobin, the substance which carries oxygen to body tissues. Because haemoglobin binds with carbon monoxide 200 times more strongly than oxygen, even low concentrations of carbon monoxide in air have magnified effects on the body.

It reduces the oxygen-carrying capacity of blood by an amount equivalent to the amount of haemoglobin converted to carboxyhaemoglobin.

Haemoglobin + CO → Carboxyhaemoglobin

Question 10

How can we control carbon monoxide poisoning?

Answer 10

Carbon monoxide pollution can be controlled in the following ways:

  1. By switching over from internal combustion engines to electrically powered cars.
  2. Many pollution control devices are now installed in cars. Most of these devices help reduce pollution by burning gasoline completely. Complete combustion of gasoline produces only carbon dioxide and water vapour.
    2C8H18 + 5O2→ 16CO2 + 18H2O
  3. By using substitute fuels for gasoline: Natural gas in both compressed (CNG) and liquefied (LNG) forms is now increasingly being used as fuel. Alcohols are other feasible substitutes.
  4. By using catalytic convertors:
    i. Nitrogen oxide is reduced to nitrogen and oxygen in the presence of finely divided platinum or palladium as a catalyst.
2NO  N2 + O2
2NO N2 + 2O2
  1. Carbon monoxide changes to carbon dioxide in the presence of finely divided platinum as catalyst.
    CO  CO2 + H2O

Concise Chemistry Solutions of Exercise-8(B),Chapter-8 Atmospheric Pollution Class-9 

Acid Rain

Question 1

Why does rain water have pH less than 7?

Answer 1

Carbon dioxide reacts with water to form weak carbonic acid which is slightly acidic having pH about 5.6.

Hence, the pH of rain water usually ranges between 5.6 and 3.5; at times, it can be as low as 2.

Question 2

pH of acid rain is sometimes as low as 2. Explain.

Answer 2

Normal rain is only slightly acidic having pH about 5.6.

This is because carbon dioxide reacts with it to form weak carbonic acid.

CO2 + H2O → H2CO3

pH of acid rain usually ranges between 5.6 and 3.5; at times, it can be as low as 2.

Question 3

Explain the formation of acid rain due to:

(i) Oxides of sulphur

(ii) Oxides of nitrogen

Answer 3

(i) Oxides of sulphur:
Sulphur is a non-metallic element found in coal and fuel oil.

When these fuels are burned, sulphur combines with oxygen in the    air to form its gaseous oxides, sulphur dioxide (SO2) and sulphur   trioxide (SO3).
S + O2 → SO2
 2SO2 + O2 → 2SO
3
   Sulphur dioxide and sulphur trioxide react with water to form  H2SO4 which is the main cause of acid rain.
2SO2 + O2 + 2H2O →2H2SO4
   SO3 + H2O →H2SO4

(ii) Oxides of nitrogen:

Nitric acid is formed by the combination of nitrogen and oxygen.        Nitrogen and oxygen combine in the presence of thunder and           lightning. Oxides of nitrogen are also produced by internal                 combustion engines.
N2 + O2 →  2NO
Nitrogen oxide then gets oxidised in the atmosphere to nitrogen dioxide.
2NO + O2 → 2NO2
  Nitrogen dioxide combines with water to form a mixture of nitrous      acid and nitric acid.
2NO2 + H2O → HNO2 + HNO3

Question 4

What are the causes of acid rain?

Answer 4

The main causes of acid rain are the formation of mineral acids such as carbonic acid, nitric acid andsulphuric acid during rains.

Question 5

Give the impact of acid rain:

(i) on plants

(i) on soil

(iii) on water bodies

Answer 5

(i) Acid rain causes loss of nutrients from plants, thus damaging  their leaves.

(ii) It removes calcium and potassium (elements of soil), thus  making it lose its fertility which ultimately damages forests.

(iii) Acid rain has serious ecological impacts as it affects water  bodies too. Water in lakes and rivers is gradually becoming acidic  due to acid rain. This adversely affects aquatic life.

Question 6

How does a scrubber help in reducing the formation of acid rain?

Answer 6

A scrubber can also be used to reduce the formation of acid rain. It is a device which absorbs gaseous pollutants. It is used for removing sulphur dioxide from a smoke stack, and usually consists of a fine spray of water and gas rising from the stack, which is passed through the scrubber where water absorbs sulphur dioxide.

How does a scrubber help in reducing the formation of acid rain

Exercise-8(C) Green House Gases ,Selina solutions of Chapter-8 Atmospheric Pollution Class-9

Question 1

What do you understand by Green House effect?

Answer 1

Heating of the Earth and its environment due to solar radiation trapped by carbon dioxide and water vapour in the atmosphere is called greenhouse effect.

Question 2

What are green house gases? How are they responsible for global warming?

Answer 2

Gases which contribute to the greenhouse effect are called greenhouse gases. These gases are carbon dioxide, water vapour, oxides of nitrogen, methane, ozone and chlorofluorocarbons.

three types of radiation

Sunlight reaching Earth consists of three types of radiation-UV radiation, visible radiation and IR radiation. As sunlight passes through the atmosphere, most UV radiation is absorbed by ozone; 30% of IR radiation reaches the Earth’s surface, heating it up.

As the Earth’s surface becomes hot, it starts emitting radiation with less energy than the incoming radiation and thus with longer wavelength. Some emitted IR radiation escapes from the Earth’s surface and some are absorbed by CO2, thus remaining on the Earth. Trapped radiation warms the Earth’s surface and lower layers of the atmosphere.

Question 3

State the sources and effects of the following gases:

(i) Carbon dioxide

(ii) Methane

(iii) Water vapour

Answer 3

(i) Carbon dioxide:

Sources of carbon dioxide:
  • Burning of fossil fuels such as coal, natural gas and petroleum
  • Industrial processes such as manufacture of lime and those in fermentation units
  • Biological decay of plants
  • Respiration by animals, human beings and plants

Effects of carbon dioxide:
  • Greenhouse effect and global warming.

(ii) Methane

Sources of methane:
  • Anaerobic decomposition of organic matter in soil, water and sediments
  • Incomplete combustion of fossil fuels.

Effects of methane:

  • Greenhouse effect and global warming.

(iii)  water vapour:

Sources of water vapour:
  • Burning of hydrocarbons
  • Evaporation and transpiration
Effects of water vapour:
  • Greenhouse effect and global warming.

Question 4

State the ways of reducing the presence of green house gases.

Answer 4

Ways of reducing the presence of greenhouse gases:

  • Minimise the use of automobiles: Depending on the situation, one can use a bicycle, the public transport system and car pools.
  • Plant more trees to increase green cover.
  • Avoid burning of dry leaves and wood.
  • Avoid smoking. It is illegal to smoke in public places and work places, because smoke is harmful not only for the one who is smoking but also for others sitting nearby.
  • Help people in understanding global warming; most people are unaware of it.

Question 5

State the effects of green house gases on the atmosphere.

Answer 5

Effects of global warming
  • Rise in sea level: Due to global warming, glaciers and polar ice caps have started to melt, and gradually this may lead to an increase in the sea level. This will in turn flood several coastal areas in countries such as India, Bangladesh, the Netherlands and the Maldives.
  • Global warming will cause more water to evaporate from water bodies, thus forming more water vapour. Because water vapour also contributes to the greenhouse effect, global warming will further increase.
  • Global warming can lead to changes in the rain pattern and thus shift in crop zones. For example, wheat-producing zones will shift from Russia and Canada to the less fertile polar regions.
  • Change in rain pattern due to global warming will also affect trees and plants in forests which are natural habitats of wild life. With destruction of forests, many species of wild life will also begin to die out.

Question 6

State the role of a green house in growing plants.

Answer 6

A greenhouse collects light and converts it to heat. It also stores thermal energy and helps moderate temperature and produces a controlled environment for plants to grow and thrive. It even offers protection from wind, rain, snow and other weather elements and protects fruits from invading pests and animals.

Question 7

Our atmosphere acts as a green house. Explain.

Answer 7

Our atmosphere contains greenhouse gases such as CO2, water vapour, O3, CH4, oxides of nitrogen and CFCs and allows the sunrays to come in. Sunlight reaching the Earth consists of three types of radiation-UV radiation, visible radiation and IR radiation. As sunlight passes through the atmosphere, most UV radiation is absorbed by ozone; 30% of IR radiation reaches the Earth’s surface, heating it up.

 As the Earth’s surface becomes hot, it starts emitting radiation with less energy than the incoming radiation and thus with longer wavelength. Some emitted IR radiation escapes from the Earth’s surface and some are absorbed by CO2, thus remaining on the Earth. Trapped radiation warms the Earth’s surface and lower layers of the atmosphere.

Question 8

How can we reduce global warming?

Answer 8

Ways of reducing global warming:

  • Minimise the use of automobiles: Depending on the situation, one can use a bicycle, the public transport system and car pools.
  • Plant more trees to increase green cover.
  • Avoid burning of dry leaves and wood.
  • Avoid smoking. It is illegal to smoke in public places and work places, because smoke is harmful not only for the one who is smoking but also for others sitting nearby.
  • Help people in understanding global warming; most people are unaware of it.

 

Ozone Excercise -8(D) Selina Concise Solutions of Chapter-8 Atmospheric Pollution Chemistry for ICSE Class-9 

Question 1

What is a pollutant?

Answer 1

Toxic and otherwise harmful substances which have an undesirable impact on different components of the environment and life forms are known as pollutants.

Question 2

What is the effect of the following pollutants on living beings (one in each case)?

a. Fluorides

b. Smoke particles

c. Lead

d. Mercury compounds

e. Smog

f. Nitrogen oxide

Answer 2

a. Fluorides cause destruction of vegetation and affect teeth and bones.

b. Smoke particles cause asthma and other lung diseases.

c. Lead impairs the body’s metabolic activities.

d. They cause disease like Minamata commonly found in fishermen.

e. Smog reduces visibility and induces respiratory troubles.

f. Nitrogen dioxide causes death of many animals.

Question 3

What is air pollution? How does this pollution take place?

Answer 3

Deterioration of air quality around us is called air pollution. Air pollution occurs because of the presence of gaseous pollutants such as oxides of sulphur, hydrocarbons, smoke, oxides of carbon, oxides of nitrogen, dust and particulate pollutants such as mist, spray and fumes.

Question 4

What are the components of clean, dry air?

Answer  4

Pure Air Components By Volume (% Proportion) Concentration (ppm)
Nitrogen 78.09 780900
Oxygen 20.94 209400
Inert gases
Argon 0.93 9300
Neon 18
Helium 5
Krypton 1
Xenon 1
Carbon dioxide 0.03 315
Methane 1
Hydrogen 0.5
Natural pollutants
Oxides of Nitrogen 0.52
Ozone 0.52

 

Question 5

Name some particulate pollutants.

Answer 5

Particulate pollutants are dust, smoke, mist, spray and fumes.

Question 6

Why is cigarette-smoking harmful?

Answer 6

Cigarette smoking is harmful not only for the one who is smoking but also for those sitting nearby, and so one should avoid smoking. Tobacco smoke causes lung cancer and asthma.

Question 7

What is smog? State its damaging effects.

Answer 7

A combination of oxides of nitrogen and sulphur, partially oxidised hydrocarbons and their derivatives produced by industries and automobiles form a dark, thick dust and soot-laden fog known as smog.

Damaging effect: Smog is noxious and irritating. It reduces visibility, induces respiratory troubles and can cause death by suffocation.

Photochemical smog: Damages the tissues of certain plants and even decreases the yield of citrus fruits and grapes.

Question 8

What do you understand by ppm?

Answer 8

ppm is parts per million, i.e. share in 1,000,000.

Question 9

Describe the major air pollutants. How does carbon monoxide pollute our environment?

Answer 9

Major air pollutants:

 Pollutant are Carbon monoxide, carbon dioxide, chlorofluorocarbons, lead, ozone, oxides of nitrogen, sulphur dioxide, suspended particulate matter

carbon monoxide pollute our environment

The Carbon monoxide is a highly poisonous gas.When inhaled, it passes through the lungs directly into the blood stream. There it combines with haemoglobin, the substance which carries oxygen to body tissues. Because haemoglobin binds with carbon monoxide more than 200 times more strongly than oxygen, even low concentrations of carbon monoxide in air have magnified effects on the body.

It reduces the oxygen-carrying capacity of blood by an amount equivalent to the amount of haemoglobin converted to carboxyhaemoglobin.

Haemoglobin + CO → Carboxyhaemoglobin

Because the heart and brain are two organs most sensitive to oxygen depletion, they show the most serious effects of carbon monoxide exposure.

In high concentration, carbon monoxide may kill by paralysing normal brain action.

Question 10

How do you propose to control:

(a) carbon monoxide emission

(b) SOx emission

Answer 10

(a) Carbon monoxide pollution can be controlled in the following ways:
  • By switching over from internal combustion engines to electrically powered cars.
  • Many pollution control devices are now installed in cars. Most of these devices help reduce pollution by burning gasoline completely. Complete combustion of gasoline produces only carbon dioxide and water vapour.
    2C8H18 + 5O2 → 16CO2 + 18H2O
  • By using substitute fuels for gasoline: Natural gas [both compressed (CNG) and liquefied (LNG)] is now increasingly being used as fuel. Alcohols are other feasible substitutes.
  • By using catalytic convertors
    Nitrogen oxide is reduced to nitrogen and oxygen in the presence of finely divided platinum or palladium as a catalyst.
    2NO  N2 + O2
    2NO2 N2 + 2O2
    Carbon monoxide changes to carbon dioxide in the presence of finely divided platinum as a catalyst.
    COCO2 + H2O
(b) SOx of sulphur emission can be reduced
  • By using coal or oil which has low sulphur content.
  • By using a scrubber, a device which absorbs gaseous pollutants.

Question 11

Give the composition, causes and effects of acid rain.

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