In qualitative analysis, when H_2S is passed through an aqueous solution of salt acidified with dil.HCl, a black precipitate is obtained. On boiling the precipitate with dil. HNO_3, it forms a solution of blue colour. Addition of excess of aqueous solution of ammonia to this solution gives

In qualitative analysis, when H_2S is passed through an aqueous soluti

1.	In qualitative analysis, when H_2S is passed through an aqueous solution of salt acidified with dil.HCl, a black precipitate is obtained. On boiling the precipitate with dil. HNO_3, it forms a solution of blue colour. Addition of excess of aqueous solution of ammonia to this solution gives
Answer» deep BLUE PRECIPITATE of`Cu(OH)_2` deep blue solution of `[Cu(NH_3)_4]^(2+)` deep blue solution of `Cu(NO_3)_2` deep blue solution of `Cu(OH)_2.Cu(NO_3)_2` Solution :A deep blue solution is formed due to the following REACTIONS : `Cu^(2+) + H_(2)S overset(dil HCl) rarr underset("(Black ppt.)")(CuS) + 2H^(+) , "" CuS + underset("(dil)")(2NHO_3) rarr underset("(Blue solution)")(Cu(NO_3)_2) + H_2S` `Cu(NO_3)_2 + 4NH_3 rarr underset("(Deep blue solution)")([Cu(NH_3)_4]^(2+)) + 2NO_(3)^(-)`