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} \rightlefthar... 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 need the molar masses. The molar mass of nitrogen (N) is 14 g/mol and that of hydrogen (H) is 1 g/mol. Since ammonia consists of one nitrogen atom and three hydrogen atoms, the molar mass of NH₃ is:
MNH3=14+(3×1)=17 g/mol
The percentage of nitrogen is given by:
Percentage of N=(Total mass of NH₃Mass of N)×100=(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
✓ 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
From graphs A, B, and C, the optimal amount of ammonium nitrate that farmers should use is around 200 kg per hectare. This is because at this level, crop yield and profit reach their maximum while the amount running off into water bodies remains minimal, thus reducing environmental impact.
