Question

An aqueous solution of 'X' reacts with sodium chloride to form white precipitate of compound 'Y' which is photosensitive. 'Y' on exposure to sunlight undergoes decomposition reaction to form metal present in compound 'X' and pungent smelling yellowish green colour gas. Identify and write the decomposition reaction.

Answer 1

X is silver nitrate and Y is silver chloride. The reaction of decomposition is as follows AgCl in presence of light = Ag + Cl2 gas.

Answer 2

We will follow the steps of the question to get to know the chemical substance involved  

For first step  

A compound X reacts with Nacl to form white precipitate, this white precipitate is the compound Y.

So X is silver nitrate which when reacted with NaCl will gives silver chloride this is compound Y. and when exposed to sunlight there will be metal decomposition which will follow the reaction as:

$\bold{\mathrm{AgCl}+\text { sunlight } \rightarrow \mathrm{Ag}+C l_{2}(\mathrm{gas}})$