Two gases P and Q both decolourise aquieous bromine buyt only one of them gives white ppt. with Tollen's reagent.P and Q likely to be:

The compound which decolourises bromine water but does not give white precipitate with Tollen's reagent.

For a gives compound There are 3 benzenoid isomer of 'X' P, Q and R for which following observation are made : (a) P is a monosubstituted benzene derivative which can give observation are made : (b) Q give position iodoform test. (c) R gives silver mirror with Tollen's reagent. Number of possible R :