c
When \(H_{2} O_{2}\) is added to an acidified solution of a dichromate \(C r_{2} O_{7}^{2-},\) a deep blue coloured complex, chromic peroxide \(C r O_{5}\left[o r C r O\left(O_{2}\right)_{2}\right]\) is formed. \(C r_{2} O_{7}^{2-}+2 H^{+}+4 H_{2} O_{2} \rightarrow\)\(\underbrace{2 C r O\left(O_{2}\right)_{2}}_{\text {Chromic peroxide }}+5 H_{2} O\)

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 \(x+(-1) 4+(-2)=0, x-6=0\) and \(x=+6\)