Identifying Complex Species in Co+2 and Ni+2 Solution with Alkaline Br2 Addition

[utkarshakash]

Homework Statement

A solution consist of Co+2 and Ni+2 ion in which excess KCN is added and in the resulting solution alkaline Br2 was added. The solution finally consist of which species?

The Attempt at a Solution

I guess some complex would be formed but how to exactly find out the complex? I don't have any idea as this does not involve any equations or mathematical approach. Any ideas?

 

[Saitama]

Homework Statement

A solution consist of Co+2 and Ni+2 ion in which excess KCN is added and in the resulting solution alkaline Br2 was added. The solution finally consist of which species?

The Attempt at a Solution

I guess some complex would be formed but how to exactly find out the complex? I don't have any idea as this does not involve any equations or mathematical approach. Any ideas?

Are there any options with the problem?

As you noticed, a complex should form in both the cases, the metal in the complex bears the same oxidation state as before.

Addition of alkaline $Br_2$ (which is basically $OBr^{-}$) serves as a test to differentiate between the two complexes. $Ni(OH)_3$ precipitates but the cobalt stays in the complex form.

 

[utkarshakash]

Are there any options with the problem?

As you noticed, a complex should form in both the cases, the metal in the complex bears the same oxidation state as before.

Addition of alkaline $Br_2$ (which is basically $OBr^{-}$) serves as a test to differentiate between the two complexes. $Ni(OH)_3$ precipitates but the cobalt stays in the complex form.

The answer is K3[Co(CN)6] and Ni2O3. Why Co+2 has been oxidised to Co+3 and how did Ni2O3 appear?