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.
What could be the pH range of aqueous solution of the gas X?

Explanation

To solve the question, we need to analyze the decomposition of copper (II) nitrate and the properties of the gas X formed during the reaction.

### Step-by-Step Solution:

1. **Identify the Reaction**:
When copper (II) nitrate (Cu(NO3)2) is heated, it decomposes into copper oxide (CuO), oxygen gas (O2), and a brown gas X. The reaction can be represented as:
\[
2 \text{Cu(NO}_3\text{)}_2 \rightarrow 2 \text{CuO} + 4 \text{NO}_2 + \text{O}_2
...