A solution of a metal ion when treated with KI gives a red precipitate which dissolves in excess KI to give a colourless solution. Moreover, the solution of metal ion on treatment with a solution of cobalt(II) thiocyanate gives rise to a deep-blue crystalline precipitate. The metal'ion is

Options

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

Answer

B

Explanation

`Hg^(2+) + 2I to Hgl_2 darr (" Scarlet re precipitate")`
`Hgl_2 + 2I to [HgI_4]^(2-)`
`Hg^(2+) Co(SCN)_2 to underset (" Deep-blue cryatallinesolid ")(Hg(SCN)_2 darr) + Co^(2+)`