What is the color of ferrous sulphate crystals? How does this color change on heating ?

Last updated date: 29th Jan 2023
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Ferrous sulphate crystals are light green in colour. They change to white on heating



Ahydrous ferrous   Ferric oxide

Sulphate (white)     (brown)

Ferrous sulphate crystals contain water molecules (FeSO4. 7H2O). On heating they lose water and anhydrous ferrous sulphate (FeSO4) is formed. So their colour changes from light green to white. On further heating, anhydrous ferrous sulphate decomposes to form ferric oxide (Fe2O3), sulphur dioxide (SO2) and sulphur trioxide (SO3). So, the gas emitted smells like burning sulphur. So, the reaction is a decomposition reaction.