O Level / IGCSE Chemistry chapter 10: Chemistry of the environment MCQs with answers
By Team Megalecture · Updated 4 Nov 2026
70 exam-style questions on Chemistry of the environment, each with the answer and a short explanation. Ten of them are below to try. The chapter test draws ten fresh questions each time and is marked the moment you finish, with your score by topic.
Ten Chemistry of the environment questions with answers
Try each one, then open the answer. These ten stay the same; the test draws new ones every time.
1. What is needed for photosynthesis to take place in a green leaf?
A
carbon dioxide and oxygen, with heat energy
B
glucose and oxygen, with chlorophyll
C
carbon dioxide and water, with chlorophyll and light energy
D
water and nitrogen, with light energy
Show answer
Answer: C. Carbon dioxide and water react using light energy absorbed by chlorophyll to make glucose and oxygen.
2. In a catalytic converter: 2CO + 2NO → 2CO2 + N2. Which statement is correct?
A
carbon monoxide is oxidised and nitrogen monoxide is reduced
B
carbon monoxide is reduced and nitrogen monoxide is oxidised
C
both gases are oxidised by the catalyst
D
nitrogen monoxide is decomposed by heat only, with no redox
Show answer
Answer: A. CO gains oxygen to become CO2 (oxidised) and NO loses oxygen to become N2 (reduced); the catalyst only speeds this up.
3. What is the percentage by mass of phosphorus in ammonium phosphate, (NH4)3PO4? (H 1, N 14, O 16, P 31)
A
9.4%
B
20.8%
C
28.2%
D
31.0%
Show answer
Answer: B. Mr = 3 × 18 + 31 + 64 = 149; % P = 31 ÷ 149 × 100 = 20.8%. 28.2% is the percentage of nitrogen, and 31.0% uses the Ar as if it were a percentage.
4. In water treatment, why is chlorine added?
A
to remove solid particles
B
to kill bacteria
C
to soften the water
D
to improve the taste
Show answer
Answer: B. Chlorination sterilises the water. Filtration removes solids; sedimentation settles larger particles.
5. Flue gas desulfurisation removes sulfur dioxide from the waste gases of a coal-fired power station. Which substance is used?
A
sodium chloride
B
carbon
C
sulfuric acid
D
calcium oxide
Show answer
Answer: D. Sulfur dioxide is an acidic oxide, so it is removed by reacting it with a basic oxide such as calcium oxide. This reduces acid rain.
6. What is the main source of sulfur dioxide in the air?
A
burning fossil fuels that contain sulfur compounds
B
the decomposition of vegetation
C
the incomplete combustion of petrol
D
the reaction of nitrogen with oxygen in car engines
Show answer
Answer: A. Sulfur compounds in fossil fuels such as coal burn to form sulfur dioxide. Decomposing vegetation gives methane and car engines give oxides of nitrogen.
7. During the treatment of the domestic water supply, what is the purpose of passing the water through carbon?
A
to remove tastes and odours
B
to remove large solid particles
C
to kill microbes
D
to make the water alkaline
Show answer
Answer: A. Carbon removes substances that cause unpleasant tastes and smells. Chlorine kills microbes; sedimentation and filtration remove solids.
8. Which substance, found in some river water, comes from fertilisers washed off farmland?
A
dissolved oxygen
B
chlorine
C
nitrates
D
carbon
Show answer
Answer: C. Nitrates and phosphates from fertilisers can be washed into rivers by rain.
9. A water sample has gone through every stage of treatment except one. It contains no solids and no live microbes, but it has an unpleasant taste and smell. Which stage was missed?
A
sedimentation
B
filtration
C
chlorination
D
treatment with carbon
Show answer
Answer: D. Carbon (activated charcoal) removes tastes and odours. Sedimentation and filtration remove solids, and chlorination kills microbes, which were already dealt with.
10. Which pollutant gas is formed inside a car engine from nitrogen and oxygen at high temperature?
A
sulfur dioxide
B
nitrogen oxides
C
methane
D
carbon monoxide
Show answer
Answer: B. At the high temperature of the engine nitrogen and oxygen from the air combine to form nitrogen oxides, a cause of acid rain and respiratory problems.
Chemistry of the environment: questions students ask
How many Chemistry of the environment MCQs are there?
70, each with the answer and a short explanation, across 3 topics: Water, Fertilisers, Air quality and climate. Every chapter test draws ten of them, so you can take it many times.
Is the O Level / IGCSE Chemistry chapter 10 test free?
Yes. The test, the answers and the explanations are free and need no sign-up. Sign in only if you want your scores kept across devices.
How is the chapter test marked?
The moment you press Finish: your score, the right answer and an explanation for every question, and the ones you got wrong saved in My mistakes to retry.
