An aqueous solution of metal nitrate 'P' reacts with sodium bromide solution to form yellow precipitate compound 'Q' which is used in photography. 'Q' on exposure to sunlight undergoes decomposition reaction to form metal present in along with a raddish brown gas. Identify 'P' and 'Q' Write balanced chemical equation for the chemical reaction. List two categories in which this reaction can be placed.

Explanation

(i) P is silver nitrate, `AgNO_(3)`.
Q is silver bromide, `AgBr`.
(ii) `AgNO_(3)(aq)+NaBr(aq)overset("Sunlight")(to)underset("(Q)")underset("Silver bromide")(AgBr(s))+NaNO_(3)(aq)`
`2AgBroverset("Sunlight")(to)2Ag+underset("(Brown gas)")underset("Bromide")(Br_(2))`
(iii) Decomposition of silver bromide can be put under two categories :
(a) Decomposition reaction.
(b) Photochemical reaction.