Which of the following statements with regard to heating of lead nitrate powder over a flame are correct? 1. Brown fumes of NO2 are released. 2. Colourless O2 gas is released. 3. It is an example of oxidation reaction. 4. It is an example of thermal decomposition used for the production of NO2 gas. Select the correct answer using the code given below.

The correct answer is Option 1. The heating of lead nitrate [2Pb(NO3)2] is a classic example of a thermal decomposition reaction. When heated, lead nitrate breaks down into lead (II) oxide (PbO), nitrogen dioxide (NO2), and oxygen (O2).

• Statement 1 is correct: The reaction produces reddish-brown fumes of nitrogen dioxide (NO2).
• Statement 2 is correct: Oxygen (O2) is also evolved, which is a colorless and odorless gas.
• Statement 3 is incorrect: While redox occurs internally, the reaction is primarily classified as a decomposition reaction, not simply an oxidation reaction.
• Statement 4 is incorrect: Although it is thermal decomposition, it is typically a laboratory demonstration of decomposition rather than a standard commercial method for the "production" of NO2 gas.

The chemical equation is: 2Pb(NO3)2 (s) → 2PbO (s) + 4NO2 (g) + O2 (g). Thus, statements 1 and 2 are the most accurate descriptions of the observations.