Ammonia produced by the Haber process can be converted into nitric acid, which is then reacted with ammonia to form ammonium nitrate. Explain why ammonium nitrate is a suitable source of nitrogen for use in NPK fertilisers.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
NPK fertilisers improve agricultural productivity by supplying plants with essential elements. Nitrogen-containing compounds are a key component of these fertilisers.
Model answer (4 marks)
Plants require nitrogen for growth, so a nitrogen source is essential for fertilisers.
Ammonium nitrate is a nitrogen compound, providing nitrogen in both the ammonium (NH4+) and nitrate (NO3–) ions.
It is highly soluble in water, allowing it to be taken up by plant roots from the soil solution.
Its high nitrogen content (≈ 34 % N) means it supplies a large amount of nitrogen per unit mass, making it an efficient fertiliser.
Ammonium nitrate is a nitrogen compound, providing nitrogen in both the ammonium (NH4+) and nitrate (NO3–) ions.
It is highly soluble in water, allowing it to be taken up by plant roots from the soil solution.
Its high nitrogen content (≈ 34 % N) means it supplies a large amount of nitrogen per unit mass, making it an efficient fertiliser.
Examiner tips
- State the role of nitrogen for plants first. Mention both ions to show it is a nitrogen source. Highlight solubility and high nitrogen content. Use exact terminology (ammonium, nitrate, soluble).
Common mistakes
- Forgetting to mention both NH4+ and NO3– as nitrogen sources. Claiming it is insoluble or underestimating its nitrogen content. Using vague terms like "good for plants" without linking to nitrogen uptake.
Mark scheme (4 marks)
- Plants need nitrogen to grow / nitrogen is an essential element for plant growth
- Ammonium nitrate contains nitrogen / is a nitrogen compound
- Ammonium nitrate is soluble (in water) / can be absorbed by plant roots (from soil solution)
- Ammonium nitrate has a high nitrogen content / provides nitrogen from two sources (ammonium ion and nitrate ion)
Key terms in this question
NPK fertilisers · ammonium nitrate · nitrogen · Haber process
Related
- All AQA GCSE Chemistry (8462) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
More The Haber process and the use of NPK fertilisers (Chem only) questions
- NPK fertilisers contain compounds of nitrogen, phosphorus and potassium. Explain…
- The Haber process is used to manufacture ammonia, which can be used to make NPK …
- A company manufactures NPK fertilisers using ammonia from the Haber process. Exp…
- A farmer uses an NPK fertiliser to increase crop yields. The NPK fertiliser cont…