(i) P is ferric chloride. It is a deliquescent salt that gives yellow solution when dissolved in water. On reaction with sodium hydroxide, it forms reddish-brown precipitate of ferric hydroxide.
(ii) Q is ammonium chloride. It is a white crystalline solid. It is soluble in water. When heated with sodium hydroxide, it liberates pungent-smelling ammonia gas.
(iii) R is ferrous sulphate. On heating, it turns reddish brown, forming ferric oxide. Aqueous ferrous sulphate reacts with barium chloride to form a white precipitate of barium sulphate, which is insoluble in mineral acids.