- Most sulphate salts do not decompose by heat. For instance, sodium sulphate, potassium sulphate, and calcium sulphate are not decomposable by heat.
- Only certain sulphate salts are decomposed by heat when heated strongly.
- For instance:
- Strong heating of green crystal iron (II) sulphate will release steam, sulphur dioxide, sulphur trioxide and leave behind a reddish solid iron (III) oxide residue. The steam released comes from the hydrated water of the crystallize salt.2FeSO4•7H2O → Fe2O3(p) + SO2(g) + SO3(g) + 14H2O(g)
- Meanwhile, zinc sulphate, copper (II) sulphate, and iron (III) sulphate decompose when heated strongly to evolve sulphur trioxide gas and form a metal oxide.
ZnSO4 → ZnO + SO3
Copper (II) sulphate
CuSO4 → CuO + SO3
Iron (III) sulphate
Fe2(SO4)3→ Fe2O3 + 3
- When ammonium sulphate is heated strongly, this white solid sublimate and is decomposed to form ammonia gas and sulphuric acid. vapour
(NH4)2SO4 → NH3 + H2SO4