I am a compound of lead. I decompose on heating to give brown fumes of a gas and a yellow residue with another colourless gas. Who am I?PbI2PbOPb(NO3)2CaCO3

To determine which compound you are, we can analyze the decomposition reactions of the provided options upon heating:

1. PbI2 (Lead(II) iodide): When heated, lead(II) iodide decomposes to form lead(II) oxide (a yellow solid) and iodine vapor (which can appear as brown fumes). The reaction can be represented as: $2 \text{PbI}_2 \rightarrow 2 \text{PbO} + \text{I}_2 + \text{I}_2(g)$ This fits the description given in the question.

2. PbO (Lead(II) oxide): This compound does not decompose further upon heating; it remains as lead(II) oxide.

3. Pb(NO3)2 (Lead(II) nitrate): Upon heating, lead(II) nitrate decomposes into lead(II) oxide (yellow solid), nitrogen dioxide (brown gas), and oxygen. The reaction is: $2 \text{Pb(NO}_3\text{)}_2 \rightarrow 2 \text{PbO} + 4 \text{NO}_2(g) + \text{O}_2(g)$ This also gives brown fumes but lacks the yellow residue mentioned in the question.

4. CaCO3 (Calcium carbonate): Heating calcium carbonate decomposes into calcium oxide and carbon dioxide: $\text{CaCO}_3 \rightarrow \text{CaO} + \text{CO}_2(g)$ This reaction does not yield brown fumes or a yellow residue; thus, it does not fit the description.

Final Answer

You are PbI2 (Lead(II) iodide), as it decomposes on heating to produce brown fumes of iodine gas and a yellow residue of lead(II) oxide.