2023 · Q33
Which one of the following statements with regard to heating of lead nitrate powder over a flame are correct?
- 1Brown fumes of NO are released.
- 2Colourless O2 gas is released.
- 3It is an example of oxidation reaction.
- 4It is an example of thermal decomposition used for the production of NO2 gas.
Select the correct answer using the code given below.
General KnowledgeChemistry
- A1 and 2
- B2, 3 and 4
- C1, 3 and 4
- D2 and 4 only
Explanation
Statement 1 is false: the brown fumes are nitrogen dioxide (NO2), not colourless NO — the reaction is 2Pb(NO3)2 -> 2PbO + 4NO2 + O2. Statement 2 is true: colourless oxygen gas is evolved. Statement 3 is false: the reaction is classified as thermal decomposition (a single reactant breaking down on heating), not as an oxidation reaction. Statement 4 is true: it is a classic thermal decomposition used to generate NO2. Hence only statements 2 and 4 are correct.