In the reaction $2{\text{KMnO}}_4+3{\text{H}}_2{\text{SO}}_4+5{\text{H}}_2{\text{O}}_2\to {\text{K}}_2{\text{SO}}_4+2{\text{MnSO}}_4+8{\text{H}}_2\text{O}+5{\text{O}}_2$, what is the role of ${\text{H}}_2{\text{O}}_2$?

Solution

1. Observe the oxidation state of oxygen in ${\text{H}}_2{\text{O}}_2$, which is $-1$.
2. Observe the oxidation state of oxygen in the product ${\text{O}}_2$, which is $0$.
3. Since the oxidation state increases, ${\text{H}}_2{\text{O}}_2$ undergoes oxidation.
4. A substance that undergoes oxidation acts as a reducing agent.
5. Hence the answer is (B).