Name the gas evolved in each of the following cases
Action of heat on mercuric oxide.

Explanation

To solve the question regarding the gas evolved during the action of heat on mercuric oxide, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the substance**: The substance in question is mercuric oxide, which is represented by the chemical formula \( \text{HgO} \). It is a red solid.

2. **Understand the process**: When mercuric oxide is heated, it undergoes a decomposition reaction. This means that it breaks down into simpler substances when exposed to heat.

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