Question

What is the color of ferrous sulphate crystals? How does this color change after heating? Name the products formed on strongly heating ferrous sulphate crystals. What type of chemical reaction occurs in this type of change.

Answer 1

The color of ferrous sulphate crystals is green.

 

Ferrous sulphate crystals contain water molecules (FeSO₄. 7H₂O). On heating, ferrous sulphate crystals 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. 

 

In this reaction, the single reactant FeSO₄ decomposes to form three different products. So, the reaction is a decomposition reaction.

 

$2FeSO_{4}(s) \rightarrow Fe_{2}O_{3}(s) + SO_{2}(g) + SO_{3}(g)$

Ahydrous ferrous     Ferric oxide

Sulphate (white)      (brown)