FeCl3 reacts with phenol and give violet or blue color. Tollens reagent react with Aldehyde, terminal alkyne, and terminal hydroxy ketones.  Chloroform in basic medium reacts with Phenols as well as Primary amines and give offensive odor. Nitrous acid reacts with primary amine specially aromatic in nature and undergo coupling reaction to give dyes.P-3,4; Q-4; R-1,2; S-1,5.