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 darr` ( scarlet red precipitate )
` Hgl_2 +2I^(-) to [Hgl_4]^(2-)`
` Hg^(2+) +Co (SCN)_2 to underset("(Deep - blue cryataline solid )")(Hg (SCN)_2 darr + Co^(2+))`