Lead nitrate on heating gives
- A.PbO2 and NO2
- B.PbO and NO2
- C.PbO and NO
- D.PbO2 and NO
Correct answer
Explanation
The correct answer is B, PbO and NO2. Lead nitrate decomposes on heating into lead(II) oxide, nitrogen dioxide and oxygen.
The balanced equation is 2Pb(NO3)2 → 2PbO + 4NO2 + O2. It is a classic thermal decomposition reaction taught in Class 10. When white lead nitrate crystals are heated in a dry test tube, they crackle (decrepitation), brown fumes of nitrogen dioxide appear, oxygen is released, and a yellow residue of lead monoxide (PbO) is left behind. Lead stays in the +2 state throughout, which is why the oxide formed is PbO and not PbO2.
Option A is wrong because lead is not oxidised to the +4 state, so PbO2 does not form. Option C is wrong because the brown gas given off is NO2, not colourless NO. Option D is wrong on both counts: neither PbO2 nor NO is a product.
Exam tip: heating lead nitrate = brown NO2 fumes + yellow PbO residue + O2; a standard example of a decomposition reaction.
Practice Questions
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