10.11 NPK fertilisers
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Which three elements are supplied by NPK fertilisers?
Choose one answer.
Correct Not quite: the answer is Nitrogen, phosphorus and potassium
Mark scheme
D
Model answer
D: nitrogen, phosphorus and potassium.
Name the two substances that react to make ammonium nitrate, and write the equation.
Mark scheme
- ammonia and nitric acid (1)
- NH3 + HNO3 → NH4NO3 (1)
Model answer
Ammonia and nitric acid: NH3 + HNO3 → NH4NO3.
Explain why phosphate rock is treated with acid before being used as a fertiliser.
Mark scheme
- phosphate rock is insoluble (1)
- acid converts it into soluble phosphates that plants can absorb (1)
Model answer
Phosphate rock is insoluble, so it is treated with acid to make soluble compounds that plants can take up.
Write a balanced equation for the formation of ammonium sulfate from ammonia and sulfuric acid.
Mark scheme
- correct formulae (1)
- 2NH3 + H2SO4 → (NH4)2SO4 (1)
Model answer
2NH3 + H2SO4 → (NH4)2SO4
Give two differences between making ammonium sulfate in the laboratory and in industry.
Mark scheme
any two from:
- lab is small scale; industry large scale (1)
- lab is a batch process; industry continuous (1)
- lab uses bought solutions; industry makes raw materials on site / more stages (1)
Model answer
The laboratory makes small amounts in a batch process from bought solutions, while industry uses a continuous process on a huge scale, making its own ammonia and sulfuric acid.
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