Hydrous ferrous sulphate crystals are heated in a boiling tube for few seconds. Water droplets are seen in the inner sides of test tube and the colour of the crystals changes. On continuous heating a colourless gas X with smell of burning sulphur is evolved and a residue Y is obtained.
Identify the gas X and the residue Y formed.

Explanation

To solve the problem, we need to analyze the heating of hydrous ferrous sulphate (FeSO4·xH2O) and identify the products formed during the process.

### Step-by-Step Solution:

1. **Heating Hydrous Ferrous Sulphate**:
When hydrous ferrous sulphate crystals are heated, they lose water molecules (H2O) due to the heat. This is indicated by the formation of water droplets on the inner sides of the test tube.

**Hint**: Remember that heating hydrates often leads to the loss of water.
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