Potassium dichromate reacts with acidified hydrogen peroxide to form a deep blue colored compound. The oxidation state of chromium in this compound is:

Solution

1. The reaction of ${\text{K}}_2{\text{Cr}}_2{\text{O}}_7$ with ${\text{H}}_2{\text{O}}_2$ in acidic medium produces ${\text{CrO}}_5$.
2. The structure of ${\text{CrO}}_5$ is a butterfly structure containing four peroxo linkages.
3. In ${\text{CrO}}_5$, the oxidation state of $\text{Cr}$ is calculated as $x+5(-2)=0$ is incorrect due to peroxo bonds.
4. Assigning $-1$ to each of the four peroxo oxygen atoms and $-2$ to the double-bonded oxygen, we get $x+4(-1)+1(-2)=0$, so $x=+6$.
5. Hence the answer is (B).