When lead nitrate is heated, then which of the following gases is produced?

Nitrogen dioxide

The correct answer is option 1. Nitrogen dioxide.

When lead nitrate (\( \text{Pb(NO}_3\text{)}_2 \)) is heated, it undergoes a decomposition reaction. The chemical equation for the reaction is:

\[ \text{Pb(NO}_3\text{)}_2 \rightarrow \text{PbO} + \text{NO}_2 + \frac{1}{2}\text{O}_2 \]

In this reaction:

Lead nitrate (\( \text{Pb(NO}_3\text{)}_2 \)) decomposes into lead oxide (\( \text{PbO} \)), nitrogen dioxide (\( \text{NO}_2 \)), and oxygen (\( \frac{1}{2}\text{O}_2 \)).

Nitrogen dioxide (\( \text{NO}_2 \)) is a brown gas with a characteristic color. It is one of the products released during the decomposition of lead nitrate.

So, when lead nitrate is heated, nitrogen dioxide is produced along with other products.