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
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 of NH₃:
Molar mass of N = 14 g/mol
Molar mass of H = 1 g/mol × 3 = 3 g/mol
Molar mass of NH₃ = 14 + 3 = 17 g/mol
Now, the percentage by mass of nitrogen is given by the formula:
Percentage by mass of N=(molar mass of NH3mass of N)×100
Substituting the values:
Percentage by mass 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 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
Farmers should use approximately 200 kg of ammonium nitrate per hectare.
Reasons: Based on Graph B, the profit per hectare stabilizes after this amount, indicating efficient usage.
Furthermore, Graph C shows that runoff increases significantly beyond this level, which can be detrimental to the environment. Therefore, using around 200 kg maximizes crop yield while minimizing environmental impact.
