This question is about ammonia and fertilisers - AQA - GCSE Chemistry - Question 2 - 2016 - Paper 2
Question 2
This question is about ammonia and fertilisers.
(a) Ammonia is produced by a reversible reaction.
The equation for the reaction is:
$$N_2 + 3H_2 \rightleftharpoon... show full transcript
Worked Solution & Example Answer:This question is about ammonia and fertilisers - AQA - GCSE Chemistry - Question 2 - 2016 - Paper 2
Step 1
Complete the sentence.
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Answer
The forward reaction is exothermic, so the reverse reaction is endothermic.
Step 2
Calculate the percentage by mass of nitrogen in ammonia (NH₃).
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Answer
To calculate the percentage by mass of nitrogen in ammonia (NH₃), we first need the molar mass:
Molar mass of N = 14 g/mol
Molar mass of H = 1 g/mol (for 3 H: 3 x 1 = 3 g/mol)
Total molar mass of NH₃ = 14 g/mol + 3 g/mol = 17 g/mol
Now, the percentage by mass of nitrogen:
Percentage of N=(molar mass of NH3mass of N)×100
Substituting the values:
Percentage of N=(1714)×100≈82.35%
Step 3
Give the pH of a neutral solution.
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Answer
pH 7.
Step 4
Which of these ionic equations shows a neutralisation reaction?
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Answer
The correct equation that shows a neutralisation reaction is:
H⁺ + OH⁻ → H₂O.
Step 5
Name the salt produced when ammonia reacts with hydrochloric acid.
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Answer
The salt produced is ammonium chloride (NH₄Cl).
Step 6
Suggest how much ammonium nitrate farmers should use per hectare.
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Answer
From Graph A, the crop yield starts to level off after 200 kg of ammonium nitrate is used per hectare. Graph B indicates that profit also stabilizes beyond this amount, while Graph C shows a rise in runoff after around 300 kg. Therefore, farmers should aim to use approximately 200 kg of ammonium nitrate per hectare to optimize yield and minimize environmental impact. This value balances high yield with minimal runoff.
