An aqueous solution of gas (X) shows the following reactions : (i) It turns red litmus blue. (ii) When added in excess to a copper sulphate solution, a deep blue colour is obtained. (iii) On addition to a ferric chloride solution, a brown precipitate soluble in dilute nitric acid, is obtained. Identify (X) and give equations for the reactions at steps (ii) and (iii).

An aqueous solution of gas (X) shows the following reactions : (i) It

1.	An aqueous solution of gas (X) shows the following reactions : (i) It turns red litmus blue. (ii) When added in excess to a copper sulphate solution, a deep blue colour is obtained. (iii) On addition to a ferric chloride solution, a brown precipitate soluble in dilute nitric acid, is obtained. Identify (X) and give equations for the reactions at steps (ii) and (iii).
Answer» Solution :(i) (a) SINCE gas (X) turns red litmus blue, it must be basic in nature. The only important gas which is basic in character is ammonia `(NH_(3))`. Thus, (X) may be ammonia. This is supported by the observation that it gives a deep blue colour with copper sulphate solution. (b) Having identified that the gas (X) is ammonia, the reactions at steps (ii) and (iii) may be explained as follows: (ii) With copper sulphate solution, it gives a deep blue colour due to the formation of tetrammine copper (II) COMPLEX. `CuSO_(4) + underset(underset((X))("Ammonia"))(4NH_(3)) rarrunderset(underset("(Deep blue colour)")("Tetramminecopper (II) sulphate"))([Cu(NH_(3))_(4)] SO_(4))` (iii) With FERRIC chloride solution, (X) gives a brown PPT. of ferric hydroxide which dissolves in dilute nitric acid to form ferric nitrate. `NH_(3) + H_(2)O rarr NH_(4)^(+) + OH^(-)` `FeCl_(3) + 3 OH^(-) rarr underset(underset(("Brown ppt."))("Ferric hydroxide"))(Fe(OH)_(3)) + 3 Cl^(-)`