Inorganic reactions
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What happens when iron(II) sulphate is heated on its own? Please give the reaction.
Igloo writes ....
Iron(II) sulphate is normally found in its hydrated form, FeSO4.7H2O
On gentle heating this green solid turns white as the water of crystallisation is evolved as steam:
FeSO4.7H2O(s) -> FeSO4(s) + 7H2O(l)
On stronger heating the anhydrous white solid darkens as iron(III) oxide is formed. Sulphur dioxide and sulphur trioxide are evolved during this decomposition:
FeSO4(s) -> Fe2O3(s) + SO2(g) + SO3(g)
Notice that this second stage involves redox as well as thermal decomposition.
The sulphur trioxide reacts with water given off to form sulphuric acid. This acid used to be called 'vitriolic acid' and long ago was made by heating hydrated sulphates. Hence the old fashioned name of green vitriol for iron(II) sulphate.
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updated: 28 January 2006
