Fertilisers (WJEC GCSE Chemistry)
Revision Note
Fertilisers
What are fertilisers?
Fertilisers contain substances that plants need to grow healthily and are used in agriculture
Nitrogenous fertilisers contain a source of nitrogen as well as minerals such as potassium and phosphorus
Nitrogen makes chlorophyll, protein and promotes healthy leaves
Potassium promotes growth and healthy fruit and flowers
Phosphorus promotes healthy roots
Fertiliser compounds contain the following water soluble ions:
Ammonium ions, NH4+ and nitrate ions, NO3-, are sources of soluble nitrogen
Phosphate ions, PO43- are a source of soluble phosphorus
Most common potassium compounds dissolve in water to produce potassium ions, K+
Table of common fertiliser compounds
Name | Formula |
---|---|
Ammonium nitrate | NH4NO3 |
Ammonium phosphate | (NH4)3PO4 |
Potassium sulfate | K2SO4 |
Ammonium sulfate | (NH4)2SO4 |
Ammonium salts and nitrates are commonly used as fertilisers
Different fertilisers contain different amounts of fertiliser compounds so each contains different proportions of nitrogen, potassium and phosphorous
Producing fertilisers
Fertilisers such as ammonium nitrate are produced by a neutralisation reaction and an ammonium salt is formed
The salt is the fertiliser
Ammonia is a gaseous alkali that reacts with nitric acid to form ammonium nitrate:
NH3 (g) + HNO3 (aq) → NH4NO3 (s)
Ammonia also reacts with sulfuric acid to form ammonium sulfate:
2NH3 (g) + H2SO4 (aq) → (NH4)2SO4 (s)
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