An aqueous blue coloured solution of a transition metal sulphate reacts with `H_(2)S` to give a black precipitate. The black precipitate dissolves in `50%` nitric acid forming a blue coloured solution. The blue solution on treatment with KI in weakly acidic medium turns yellow`//` brown and produces a white precipitate. Identify the transition metal ion from the following ions.

Options

A. `Co^(2+)`
B. `Cu^(2+)`
C. `Hg^(2+)`
D. `Pb^(2+)`

Answer

2

Explanation

`CuSO_(4)+H_(2)S rarrCuSdarr("black")+H_(2)SO_(4)`
`CuS+2HNO_(3)rarrCu(NO_(3))_(2)("blue solution")+NO+S+H_(2)O`
`2Cu^(2+)+4I^(-) rarrCu_(2)I_(2) darr("white")+I_(2) uarr ("colour of solution is yellow"//"brown")`