Question

Oxidation state of Cr in K2[Cr(CN)2(O2)(O2)NH3])

Answer 1

IUPAC name of K₂[Cr(CN)₂(O)₂(O₂)(NH₃)] is potassium amminedicyanodioxoperoxocromate(VI)

Well, Let's check it is true or false.
oxidation state of oxo, (O) = -2
oxidation state of peroxo (O₂) = -2
oxidation state of ammimo (NH₃) = 0
oxidation state of dicyano (CN) = -1

Now, [(Cr(CN)₂(O)₂(O₂)(NH₃)]⁻⁻ + K²⁺
Let oxidation state of Cr = x
x +2(-1) + 2(-2) + (-2) = -2
x = +6

Answer 2

The IUPAC name for this compound is :

Potassiumaminedicyanodioxoperoxochromate (IV)

In this compound the breakdown of the charges of each elements are:

K = +1 × 2 = 2

CN = - 1 ×2 = - 2

O = - 2 × 2 = - 4

NH₃ = 0 since it is a neutral ligand.

O₂ = 0 since it is a neutral ligand.

Let the the oxidation state of Chromium = x since chromium ions are positive.

The total charges equals zero since a neutral compound is formed.

CALCULATIONS :

2 + - 2 + - 4 + 0 + 0 + x = 0

-4 + x = 0

x = + 4

The oxidation state of chromium ions is thus + 4