Identify reducing agent in following reaction

$$\mathrm{H}_2 \mathrm{O}_{2(\mathrm{ag})}+\mathrm{ClO}_{4(\mathrm{aq})}^{-} \rightarrow \mathrm{ClO}_{2(\mathrm{aq})}^{-}+\mathrm{O}_{2(\mathrm{g})}$$

Identify reductant in following reaction.

$$\mathrm{H}_2 \mathrm{~S}+\mathrm{NO}_2 \rightarrow \mathrm{H}_2 \mathrm{O}+\mathrm{NO}+\mathrm{S}$$

Oxidation state of Cr in potassium dichromate is

What is the value of '$$\mathrm{x}$$' in order to balance the following redox reaction by ion electron method? $$\quad \mathrm{x} \mathrm{H}_2 \mathrm{O}_2+\mathrm{ClO}_4 \rightarrow \mathrm{xO}_2+\mathrm{ClO}_2+2 \mathrm{H}_2 \mathrm{O}$$