Name the gas evolved in each of the following cases
Action of heat on blue vitriol.

Explanation

### Step-by-Step Solution:

1. **Identify Blue Vitriol**:
- Blue vitriol is the common name for hydrated copper(II) sulfate, which has the chemical formula CuSO₄·5H₂O. This indicates that it contains five molecules of water of crystallization.

2. **Understand the Process of Heating**:
- When blue vitriol is subjected to heat, it undergoes a thermal decomposition reaction. This means that the compound breaks down into simpler substances when heated.

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