Question 1Multiple choice · 1 markA* challenge
What is the percentage by mass of nitrogen in ammonium nitrate, NH₄NO₃ (Mr = 80)?
- A 17.5 %
- B 28 %
- C 35 %
- D 70 %
Show answer
Answer: C
Free Fertilisers questions for IGCSE Chemistry (0620), part of Chemistry of the environment. Each question has the answer and the marking points an examiner would look for.
Generate a full Fertilisers worksheet →All Chemistry of the environment questionsWhat is the percentage by mass of nitrogen in ammonium nitrate, NH₄NO₃ (Mr = 80)?
Answer: C
Ammonium sulfate is warmed with sodium hydroxide.
Which gas is produced?
Answer: B
Which term is described by this statement?
“A fertiliser containing nitrogen, phosphorus and potassium for plant growth.”
Answer: C
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 |
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 66 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) | 17.0 kg 66/132 × 2 × 17 (2 : 1 ratio) M1 17.0 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 |
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 |
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