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:
N₂ + 3H₂ ⇌ 2NH₃
Complete the ... 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 find the percentage by mass of nitrogen in ammonia, we first determine the molar mass of NH₃:
Nitrogen (N): 1 × 14 = 14 g/mol
Hydrogen (H): 3 × 1 = 3 g/mol
Molar mass of NH₃ = 14 g/mol + 3 g/mol = 17 g/mol.
Now, the percentage by mass of nitrogen is given by:
[
\text{Percentage of N} = \left( \frac{\text{mass of N}}{\text{molar mass of NH}_3} \right) \times 100 = \left( \frac{14}{17} \right) \times 100 \approx 82.35%.
]
Step 3
Give the pH of a neutral solution.
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Answer
The pH of a neutral solution is 7.
Step 4
Which of these ionic equations shows a neutralisation reaction?
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Answer
The correct equation for 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 when ammonia reacts with hydrochloric acid is ammonium chloride (NH₄Cl).
Step 6
Suggest how much ammonium nitrate farmers should use per hectare.
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Answer
Based on the graphs A, B, and C, farmers should use around 200 kg of ammonium nitrate per hectare. This amount maximizes crop yield as seen in Graph A, while Graph B indicates that profit remains stable beyond this point. Additionally, Graph C shows that using more than 200 kg leads to increased runoff, which could contribute to environmental concerns.
