10 free IGCSE Chemistry Chemistry of the Environment questions written in the style of Cambridge Chemistry papers: 3 multiple-choice and 7 structured, each with its answer and mark scheme. 4 of them are A* challenge questions, built to catch the mistakes strong students still make.
This topic covers Water, Fertilisers, Air quality & climate. Work through the questions below, then generate a full Chemistry of the Environment paper with a fresh set every time.
Generate a full Chemistry of the Environment paper →Air pollutants come from several sources.
1 Carbon monoxide is formed by the incomplete combustion of carbon-containing fuels.
2 Oxides of nitrogen are formed when nitrogen and oxygen react in hot car engines.
3 Sulfur dioxide is the main cause of the greenhouse effect.
Which statements are correct?
Answer: B
What is the percentage by mass of nitrogen in the fertiliser CO(NH2)2?
Answer: B
Ammonium sulfate is warmed with sodium hydroxide.
Which gas is produced?
Answer: A
Ammonium sulfate is made by neutralisation.
Name the acid and alkali used to make ammonium sulfate.
Write the equation for the reaction.
State the elements essential for plant growth in NPK fertilisers.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | sulfuric acid and ammonia sulfuric acid B1 ammonia (solution) B1 | 2 |
| (b) | 2NH₃ + H₂SO₄ → (NH₄)₂SO₄ correct formulae B1 balanced B1 | 2 |
| (c) | N, P, K nitrogen, phosphorus, potassium B1 | 1 |
NPK fertilisers contain compounds of nitrogen, phosphorus and potassium.
Explain why farmers add fertilisers to the soil.
Name one compound that supplies nitrogen.
Calculate the percentage by mass of nitrogen in ammonium nitrate, NH₄NO₃. (Mr = 80)
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | replace elements removed by crops to replace the elements (nutrients) taken up by crops / to increase crop yield B1 | 1 |
| (b) | ammonium nitrate ammonium nitrate (or ammonium sulfate, ammonium phosphate) B1 | 1 |
| (c) | 35 % (2 × 14 ÷ 80) × 100 C1 35 % A1 | 2 |
This question is about fertilisers.
Name the three elements in NPK fertilisers and state why plants need them.
Ammonium sulfate, (NH₄)₂SO₄, is made by reacting aqueous ammonia with dilute sulfuric acid.
Write the equation for the formation of ammonium sulfate.
Explain why a titration method is used to prepare this salt rather than adding an excess of a solid.
Calculate the mass of ammonia needed to make 132 kg of ammonium sulfate. [Mᵣ: (NH₄)₂SO₄, 132; NH₃, 17]
Describe a test for ammonium ions and give the result.
Calculate the percentage by mass of nitrogen in ammonium sulfate.
Explain why farmers add calcium hydroxide to acidic soil, and why they do not add sodium hydroxide instead.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | nitrogen, phosphorus, potassium; for healthy growth nitrogen, phosphorus and potassium B1 essential for plant growth (proteins / roots / fruit) B1 | 2 |
| (b)(i) | 2NH₃ + H₂SO₄ → (NH₄)₂SO₄ correct formulae B1 balanced B1 | 2 |
| (ii) | both reactants are solutions, excess cannot be filtered off ammonia is a solution / both reactants are aqueous B1 so an excess could not be removed by filtration B1 | 2 |
| (iii) | 34.0 kg 132/132 × 2 × 17 (2 : 1 ratio) M1 34.0 kg A1 | 2 |
| (c) | warm with NaOH(aq); damp red litmus turns blue warm with aqueous sodium hydroxide B1 gas turns damp red litmus paper blue B1 | 2 |
| (d) | 21.2% 28/132 × 100 M1 21.2% A1 | 2 |
| (e) | neutralises acidity; NaOH too soluble/strongly alkaline/corrosive to neutralise the acid / raise pH B1 sodium hydroxide is very soluble / strongly alkaline / corrosive, so the pH would become too high B1 | 2 |
Water from rivers is treated before it is supplied to homes.
Describe the purpose of filtration and chlorination in water treatment.
Describe a chemical test for water and give the result.
Describe a physical test to show that a sample is pure water.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | remove solids; kill microbes filtration removes insoluble solids B1 chlorination kills bacteria/microbes B1 | 2 |
| (b) | anhydrous copper sulfate white → blue add anhydrous copper(II) sulfate B1 turns from white to blue (or cobalt chloride paper blue to pink) B1 | 2 |
| (c) | boils at 100 °C, melts at 0 °C boiling point exactly 100 °C B1 melting point exactly 0 °C B1 | 2 |
Incomplete combustion of fuels produces carbon monoxide.
Explain why carbon monoxide is dangerous.
State the conditions that cause incomplete combustion.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | binds to haemoglobin, toxic it combines with haemoglobin B1 reducing the oxygen carried by the blood (toxic) B1 | 2 |
| (b) | limited oxygen limited supply of oxygen/air B1 | 1 |
Clean, dry air contains nitrogen, oxygen, argon and carbon dioxide.
State the approximate percentages of nitrogen and oxygen in clean, dry air.
Name two pollutant gases from car engines and one effect of each.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | 78 %; 21 % nitrogen 78 % B1 oxygen 21 % B1 | 2 |
| (b) | CO toxic; NOx acid rain/smog carbon monoxide B1 toxic (reduces oxygen carried by blood) B1 oxides of nitrogen B1 acid rain / photochemical smog / respiratory problems B1 | 4 |
Ammonium salts react with alkalis.
Explain why farmers should not add lime (calcium hydroxide) at the same time as ammonium fertilisers.
Describe the test for ammonia.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | ammonia gas lost the alkali reacts with ammonium salts B1 ammonia gas is released, so nitrogen is lost B1 | 2 |
| (b) | damp red litmus turns blue damp red litmus paper turns blue B1 | 1 |
In the 0620 syllabus, Chemistry of the Environment covers Water, Fertilisers, Air quality & climate.
This page has 10 Chemistry of the Environment questions with answers. For more, the free generator on mentorriyaz.in builds a new Chemistry of the Environment paper with a full mark scheme each time you click.
Riyaz Shaikh has mentored IGCSE, IB and A Level students for 15+ years, one-on-one, online and in Mumbai. The hardest questions on this site are the ones he uses to find a student's weak points.
Meet Riyaz →Original Cambridge-style practice questions written for mentorriyaz.in. These are not Cambridge past paper questions, and this site is not affiliated with or endorsed by Cambridge University Press & Assessment. Updated 2026-11-04. Paper generator · mentorriyaz.in