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

Step-by-step solution

When a solution of a H g 2 + is treated with KI a red precipitate of ( H g I 2 ) is obtained which dissolves in excess KI to give a colourless solution ( H g I 4 ) 2 - . When the solution of H g 2 + is treated with a solution of cobalt (II) thiocyanate a deep blue crystalline precipitate of H g ( S C N ) 2 is formed. The reactions are as follows H g 2 + + 2 I – → H g I 2 H g I 2 ( e x c e s s ) + 2 I – → [ H g I 4 ] 2 – S o l u b l e Hg 2 + + Co ( SCN ) 2 → Hg ( SCN ) 2 Blue   crystal   line &#