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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:-

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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

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(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.

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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

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  • 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.

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