Class 8 chemistry MCQs with answers are provided here for Chapter 18, Pollution of Air and Water. These MCQs are based on the CBSE board curriculum and correspond to the most recent Class 8 chemistry syllabus. By practising these Class 8 Multiple choice questions, students will be able to quickly review all of the ideas covered in the chapter and prepare for the Class 8 Annual examinations as well as other competitive exams.
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Class 8 Pollution of Air and Water MCQs
1. Incomplete combustion of fuels releases ____ gas.
a.) NO2
b.) CO
c.) CO2
d.) SO2
Answer – (b.) CO
Explanation – Incomplete combustion of fuels produces carbon monoxide gas (CO). When inhaled, carbon monoxide is a poisonous gas because it reduces the oxygen-carrying capacity of our blood.
2. Which kind of pollutant can easily be removed from polluted water?
a.) Solid
b.) Liquid
c.) Dissolved
d.) Nutrients
Answer – (a.) Solid
Explanation – Physical or mechanical means can easily remove solid large-sized materials from polluted water as they are not dissolved in water. These can include plastics, metals, sand, and other materials.
3. Which of the following fuels causes minimum air pollution?
a.) Kerosene oil
b.) Petrol
c.) Coal
d.) Hydrogen
Answer – (d.) Hydrogen
Explanation – When hydrogen burns, it turns into water vapour. There is no release of carbon or other compounds into the atmosphere.
4. The most polluted river in the world is ____.
a.) Yamuna river
b.) Ganga river
c.) Cauvery river
d.) Chenab river
Answer – (b.) Ganga river
Explanation – Every day, approximately three million litres of sewage are discharged into the Ganges, with only about half of that being treated. The river’s waters are so polluted that it is considered one of the world’s most polluted waterways.
5. Global warming causes:
a.) Change in pressure of earth
b.) No change in temperature
c.) Increase in temperature of earth
d.) Decrease in temperature of the earth
Answer – (c.) Increase in temperature of earth
Explanation – Global warming is the gradual rise in global temperature caused by the greenhouse effect due to increased levels of carbon dioxide, CFCs, and other pollutants.
6. Which of the following methods of water purification will not kill microorganisms?
a.) Distillation
b.) Boiling
c.) Chlorination
d.) Filtration
Answer – (d.) Filtration
Explanation – Filtration is a physical method for separating insoluble contaminants from water but does not kill microorganisms.
At boiling temperatures, boiling and distillation kill all pathogens.
Pathogens such as bacteria and viruses are killed by chlorine by breaking the chemical bonds in their molecules.
7. Which of the following is/are greenhouse gas?
a.) Carbon dioxide
b.) Methane
c.) Nitrous oxide
d.) All of the above
Answer – (d.) All of the above
Explanation – Greenhouse gases trap the sun’s heat, preventing it from escaping into space and contributing to global warming.
8. The last step in the treatment of sewage is ____.
a.) Aeration
b.) Chlorination
c.) Evaporation
d.) Decantation
Answer – (b.) Chlorination
Explanation – Chlorination is the process of adding a specific amount of chlorine to water to create a residual strong enough to kill bacteria, viruses, and cysts. It is done at last just before releasing the water into the distribution system.
9. Which of the following is a natural source of air pollution?
a.) Volcanic eruptions
b.) Forest fire
c.) Smokes from industries
d.) Automobile exhausts
Answer – (a.) Volcanic eruptions and (b.) Forest fire
Explanation – Smoke from industries and automobiles from exhausts are man-made sources of pollution, as industries and automobiles are made by man.
10. Water that is fit for drinking purposes is known as ____.
a.) Potable water
b.) Sewage water
c.) Seawater
d.) Portable water
Answer – (a.) Potable water
Explanation – Potable water, also known as drinking water, is obtained from surface and ground sources and is treated to meet consumption standards.
11. Smog is a mixture of:
a.) Water and air
b.) Smoke and dust
c.) Smoke and fog
d.) Fog and dust
Answer – (c.) Smoke and fog
Explanation – Smog is composed of smoke and fog (tiny water particles suspended in the air). Smoke contains nitrogen oxides, which combine with other air pollutants and fog to form smog.
12. Which of the following is not a major source of water pollution?
a.) Agricultural waste
b.) Industrial waste
c.) Untreated sewage
d.) None of the above
Answer – (d.) None of the above
Explanation – Waste from industries and untreated sewage is released into the water as well the waste from agriculture mixed with running water causes pollution. Hence, all the options given are a major source of water pollution.
13. The gas responsible for acid rain is:
a.) NO2
b.) CO2
c.) SO2
d.) CH4
Answer – (a.) NO2 and (c.) SO2
Explanation – Acid rain results when NO2 and SO2 gas mixes with water droplets in clouds resulting in the formation of nitric and sulphuric acids, which come down as rain.
14. The Ganga Action Plan was launched by:
a.) Mahatma Gandhi
b.) Rajeev Gandhi
c.) Indira Gandhi
d.) Jawaharlal Nehru
Answer – (b.) Rajeev Gandhi
Explanation – The Ganga Action Plan was launched by Rajeev Gandhi, the then prime minister of India. The main aim of the Ganga Action Plan is to reduce the pollution levels in the river Ganga.
15. Which of the following is not a greenhouse gas?
a.) Carbon dioxide
b.) Nitrogen
c.) Methane
d.) Nitrous oxide
Answer – (b.) Nitrogen
Explanation – Greenhouse gases trap the heat and do not let it escape the atmosphere. Nitrogen gas does not have the ability to trap heat. Hence, it is not a greenhouse gas.
16. The impurities in sewage are a suspended mixture of:
a.) Organic impurities
b.) Inorganic impurities
c.) Faecal matter
d.) Food waste
Answer – (a.) Organic impurities and (b.) Inorganic impurities
Explanation – Sewage contains both organic and inorganic impurities, such as food wastes and microorganisms, faecal matter (organic), detergents (inorganic), and so on.
17. The phenomenon of trapping heat in the atmosphere is:
a.) Ozone depletion
b.) Greenhouse effect
c.) Global warming
d.) Air pollution
Answer – (b.) Greenhouse effect
Explanation – The Greenhouse effect causes an increase in the average temperature of the earth’s near-surface air and oceans.
The greenhouse effect is the process by which radiation from a planet’s atmosphere warms its surface to a temperature higher than it would be if the planet didn’t have an atmosphere.
18. Which of the following diseases is caused due to drinking contaminated water?
a.) Typhoid
b.) Polio
c.) Dengue
d.) Measles
Answer – (a.) Typhoid and (c.) Dengue
Explanation – Water-borne diseases are caused by drinking water contaminated with pathogenic microorganisms from human or animal faeces. These are spread through flies and mosquitoes as carriers.
19. Which of the following gases is responsible for an increase in global warming?
a.) Methane and CO2
b.) Methane and CO
c.) Methane and O3
d.) Methane and NO2
Answer – (a.) Methane and CO2.
Explanation – Global warming is caused by an increase in greenhouse gases in the atmosphere, such as methane and CO2. Both methane and carbon dioxide contribute significantly to global warming.
20. Which of the following steps can be taken to reduce water pollution?
a.) Planting more trees
b.) Treating sewage water before discharging
c.) Using organic fertilisers and pesticides
d.) All of the above
Answer – (d.) All of the above
Read Also:
- Causes of Water Pollution
- Prevention of Air Pollution
- Air Pollution Questions
- Water Management Questions
- Chemistry Concept Questions and Answers
- Class 8 Chemistry Chapter 18 – Pollution of Air and Water Important Questions with Answers
- Class 8 Chemistry Worksheet Chapter 18 Pollution of Air and Water – Set 1
- Class 8 Chemistry Worksheet Chapter 18 Pollution of Air and Water – Set 2
- Class 8 Chemistry Worksheet Chapter 18 Pollution of Air and Water – Set 3
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