Describe — 5 marks
A farmer in East Anglia is planning to increase crop yields on his land. He decides to use nitrogen-based fertilisers produced using the Haber process. The fertiliser will help replace nitrogen in the soil that has been depleted by previous harvests.
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(a) Describe what happens to nitrogen gas and hydrogen gas in the Haber process.
[2 marks]
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(b) Describe two reasons why the Haber process is important for global food production.
[2 marks]
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(c) Describe one environmental disadvantage of using nitrogen-based fertilisers produced by the Haber process.
[1 mark]
Show mark scheme
- (a) Nitrogen and hydrogen react together / combine
- (a) To form ammonia (or ammonium compounds / fertilisers)
- (b) Ammonia/nitrogen fertilisers replace nitrogen in soil that crops remove
- (b) Nitrogen is essential for plant growth (or protein synthesis)
- (b) Allows higher crop yields / increased food production to feed growing population
- (b) Provides a synthetic source of nitrogen without relying on natural processes
- (c) Excess fertiliser washes into water sources causing eutrophication / algal blooms
- (c) Nitrogen oxides produced during manufacture contribute to air pollution / greenhouse gas emissions
- (c) Energy-intensive process uses fossil fuels
Describe — 3 marks
A farmer in East Anglia is planning to increase crop yields by applying nitrogen-based fertilisers produced using the Haber process. The farmer needs to understand how ammonia is manufactured and why this process is important for modern agriculture.
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(a) Describe the raw materials used in the Haber process.
[1 mark]
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(b) Describe the conditions required for the Haber process to operate efficiently.
[1 mark]
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(c) Describe why ammonia produced by the Haber process is converted into other nitrogen compounds before being used as fertilisers.
[1 mark]
Show mark scheme
- (a) Nitrogen (from air/atmosphere) and hydrogen (from natural gas/methane/hydrocarbons) are the raw materials
- (b) High temperature (around 450°C) and high pressure (around 150-200 atm) and a catalyst (iron) are required
- (c) Ammonia is converted to nitrates/nitric acid/ammonium salts because these compounds are more suitable for use as fertilisers / ammonia is a gas and less stable / nitrates are more easily absorbed by plants / ammonia is toxic to plants
Define — 3 marks
A farmer is considering using nitrogen-based fertilisers produced by the Haber process to increase crop yields. The farmer needs to understand the key concepts involved in fertiliser production and why this process is important for modern agriculture.
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(a) Define what is meant by a 'fertiliser'.
[1 mark]
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(b) Define the term 'reversible reaction' in the context of the Haber process.
[1 mark]
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(c) Define what is meant by 'nitrogen fixation' and explain why this process is essential for agriculture.
[1 mark]
Show mark scheme
- (a) A substance that provides essential nutrients (nitrogen/phosphorus/potassium) to plants
- (b) A chemical reaction that can proceed in both forward and reverse directions / reactants can form products and products can reform reactants
- (c) The conversion of atmospheric nitrogen (N₂) into nitrogen compounds (ammonia/nitrates) that plants can use
- (c) This is essential because plants cannot directly use N₂ from the atmosphere and need usable nitrogen compounds for protein synthesis and growth
Describe — 2 marks
A farmer is planning to increase crop yields on their land. They decide to use nitrogen-based fertilisers produced using the Haber process. The farmer wants to understand how this industrial process works and why it is important for modern agriculture.
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Describe what happens to nitrogen gas and hydrogen gas in the Haber process.
[2 marks]
Show mark scheme
- {'mark': 1, 'description': 'Nitrogen and hydrogen react together / combine'}
- {'mark': 1, 'description': 'To form ammonia (or they produce ammonia)'}
Calculate — 2 marks
A fertiliser factory uses the Haber process to produce ammonia. The reaction is: N₂ + 3H₂ → 2NH₃. In one production run, 14 tonnes of nitrogen gas reacts with excess hydrogen.
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(a) Calculate the relative formula mass (Mᵣ) of ammonia (NH₃). (Relative atomic masses: N = 14, H = 1)
[1 mark]
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(b) Calculate the maximum mass of ammonia that can be produced from 14 tonnes of nitrogen.
[1 mark]
Show mark scheme
- (a) 14 + (3 × 1) = 17
- (b) 17 tonnes (accept 17)
GCSE Perfect