13. A salt mixture containing compounds [A, yellow solid] and [B, colourless solid] gives a lilac colour in the flame test. Its aqueous solution : A salt mixture containing compounds [A, yellow solid] and [B, colourless solid] gives a lilac colour in the flame test. Its aqueous solution : (a) is alkaline. On passing H2S, it gives a black precipitate [C] which is soluble only in aqua regia. Evaporation of the aqua regia solution followed by extraction with dilute HCl and treatment with SnCl2 yields a greyish-black precipitate. (a) is alkaline. On passing H2S, it gives a black precipitate [C] which is soluble only in aqua regia. Evaporation of the aqua regia solution followed by extraction with dilute HCl and treatment with SnCl2 yields a greyish-black precipitate. (b) On adding NH4OH, gives and orange brown precipitate [D]. The Na2CO3 extract of the salt mixture gives the following tests : (b) On adding NH4OH, gives and orange brown precipitate [D]. The Na2CO3 extract of the salt mixture gives the following tests : (i) On acidification with dilute HNO3 followed by addition of AgNO3 gives a yellow precipitate which is insoluble in NH3. (i) On acidification with dilute HNO3 followed by addition of AgNO3 gives a yellow precipitate which is insoluble in NH3. (ii) On acidification with dilute HCl followed by shaking with FeCl3 and CCl4 gives a violet colouration in CCl4 layer. (ii) On acidification with dilute HCl followed by shaking with FeCl3 and CCl4 gives a violet colouration in CCl4 layer. Identify compounds [A] and [B] of the mixture and the precipitates [C] and [D]. Identify compounds [A] and [B] of the mixture and the precipitates [C] and [D]. Solution: Solution: [A] = HgO; [B] = KI; [C] = HgS; [D] = NH2Hg2I3 [A] = HgO; [B] = KI; [C] = HgS; [D] = NH2Hg2I3