Question

A white salt of lead on heating decomposes to give brown fumes and a yellow residue in left
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Answer 1

LEAD NITRATE

For details have a look at the picture below:

Answer 2

The white salt is lead nitrate, Pb(NO3)2. The brown fumes are of Nitrogen dioxide gas and the yellow residue left is of lead oxide.

Pb(NO3)2 + heating-------> PbO + NO2 + O2