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.
What is the colour of the crystals before and after mild heating?

Explanation

To answer the question regarding the color of hydrous ferrous sulphate crystals before and after mild heating, we can follow these steps:

### Step 1: Identify the Initial Color of Hydrous Ferrous Sulphate
- Hydrous ferrous sulphate, which has the formula FeSO4·xH2O (where x represents the number of water molecules), is typically green in color when it is in its hydrated form.

### Step 2: Observe the Changes During Mild Heating
- When hydrous ferrous sulphate crystals are heated, they lose water molecules. This process is called dehydration. As the crystals lose water, they change color.

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