GCSE Chemistry (AQA)

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Making NPK Fertilisers

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Using resources The Haber process and the use of NPK fertilisers

Making NPK Fertilisers

8:05 Manufacture and Use of NPK fertilisers
Spec 4.10.4.2
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  • Fertilizers, including NPK fertilizers, are made from raw materials and processes.
  • NPK fertilizers are soluble compounds containing nitrogen, phosphorus, and potassium.
  • Ammonia is used to manufacture ammonium salts and nitric acid, both important nitrogen sources for fertilizers.
  • Ammonium salts are produced by reacting ammonia with an acid, resulting in a neutralization reaction.
  • Ammonia plus phosphoric acid forms ammonium phosphate and water, containing nitrogen and phosphate ions.
  • Ammonia can also react with nitric acid to produce ammonium nitrate and water.
  • Nitric acid is produced by oxidizing ammonia.
  • Potassium and phosphorus are obtained by mining minerals.
  • Potassium is found in potassium chloride and potassium sulfate, both soluble in water and usable as fertilizers.
  • Phosphorus is found as phosphate rock, which is insoluble and must be treated with chemicals to release phosphate ions.
  • Phosphate rock is treated with nitric or sulfuric acid to produce soluble salts for fertilizers.
  • Different acids produce different fertilizer compounds from phosphate rock.
  • Ammonia can react with phosphoric acid to produce ammonium phosphate, a soluble NPK salt.
  • NPK fertilizers can be made in labs or industrially.
  • Lab production uses small-scale apparatus and is slow, producing small amounts.
  • Industrial production is continuous, using integrated processes to produce large amounts quickly.
  • Industrial processes are continuous, while lab methods are batch processes.
  • For exams, students should compare industrial and lab production of fertilizers.
  • Example: Ammonium sulfate crystals can be made in labs or factories, with industrial methods being faster and producing more.

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