On heating blue coloured powder of copper (II) nitrate in a boiling tube, copper oxide (black), oxygen gas and a brown gas X is formed.
Identify the brown gas X evolved.

Explanation

To solve the problem, we need to identify the brown gas (X) that is evolved when copper (II) nitrate is heated. Here’s the step-by-step solution:

### Step 1: Write the chemical formula for copper (II) nitrate.
Copper (II) nitrate is represented by the chemical formula \( \text{Cu(NO}_3\text{)}_2 \).

### Step 2: Understand the decomposition reaction.
When copper (II) nitrate is heated, it undergoes thermal decomposition. This means it breaks down into simpler substances.

...