Nitrogen, Phosphorus and Potassium
Chemistry: AQA GCSE Higher, topic 10.4.10
Nitrogen, Phosphorus and Potassium
Nitrogen, phosphorus and potassium can be used in fertilisers. We will look at the sources and production of such fertilisers.
Production of ammonium nitrate
- The nitrogen-containing compounds that are found in fertilisers are made using ammonia and nitric acid to produce ammonium nitrate:
- Ammonia + nitric acid → ammonium nitrate
- NH3(aq) + HNO3(aq) → NH4NO3(aq)
Nitrogen from two sources
- Because it contains nitrogen from two sources, ammonium nitrate is exceptionally rich in nitrogen.
- This means that it is ideal for use in fertilisers.
Phosphate rock
- Phosphate rock is a source of insoluble phosphorus that is obtained by mining.
- Useful soluble products can be obtained by treating phosphate rock with different acids.
- This includes the phosphate-containing compounds found in fertilisers.
Treatments of phosphate rock
- Treatment of phosphate rock with nitric acid yields phosphoric acid and calcium nitrate.
- Treatment of phosphate rock with sulfuric acid yields single superphosphate (a mixture of calcium sulfate and calcium phosphate).
- Treatment of phosphate rock with phosphoric acid yields triple superphosphate (calcium phosphate).
Sources of potassium
- There are two main soluble sources of potassium that can be used as fertilisers in their raw form:
- Potassium chloride
- Potassium sulfate
- Both of these soluble sources of potassium are extracted using mining.
Test yourself on Nitrogen, Phosphorus and Potassium
Why is phosphate rock treated with acid before it is used in fertilisers?
Why does treating phosphate rock with phosphoric acid produce a fertiliser richer in phosphate than treating it with sulfuric acid?
Select the true statement in each pair about treating phosphate rock