JEE Advanced 2013 Paper 2

An aqueous solution of a mixture of two inorganic salts, when treated with dilute HCl, gave a precipitate (P) and a filtrate(Q).The precipitate P was found to dissolve in hot water. The filtrate(Q) remained unchanged, when treated with H‌2S in a dilute acid medium. However,it gave a precipitate (R) with H‌2S in an ammonical medium. The precipitate R gave a coloured solution(S), when treated with H‌2O‌2 in an aqueous NaOH medium.