In acidic medium, H2O2 changes to CrO5 which has two (-O-O-) bonds. Oxidation state of Cr in CrO5 is
(c) When H2O2 is added to an acidified solution of a dichromate , a deep blue coloured complex, chromic powder, CrO5 [or CrO(O2)2] is formed.
This deep Blue coloured complex has the following structure.
Oxidation state of Cr is +6 due to the presence of two peroxide linkages, which can be calculated as
Cr peroxide normal
X + (-1)4 + (-2) = 0