What is the change in oxidation number of $$\mathrm{Cr}$$ in the following redox reaction?

$$3 \mathrm{H}_2 \mathrm{O}_{2(\mathrm{aq})}+\mathrm{Cr}_2 \mathrm{O}_{7 \text { (aq) }}^{2-}+8 \mathrm{H}_{(\mathrm{aq})}^{+} \longrightarrow 3 \mathrm{O}_{2(\mathrm{~g})}+2 \mathrm{Cr}^3+7 \mathrm{H}_2 \mathrm{O}$$

What is the oxidation number of sulfur in $$\mathrm{H}_2 \mathrm{SO}_5$$ ?

Identify the elements undergoing reduction and oxidation respectively in the following redox reaction.

$$3 \mathrm{H}_3 \mathrm{AsO}_{3(\mathrm{aq})}+\mathrm{BrO}_{3(\mathrm{aq})}^{-} \rightarrow \mathrm{Br}_{(\mathrm{aq})}^{-}+3 \mathrm{H}_3 \mathrm{AsO}_4$$

What is the value of $$x$$ in order to balance following redox reaction?

$$\mathrm{Mn}_{(\mathrm{aq})}^{2+}+x \mathrm{ClO}_{3(\mathrm{aq})}^{-} \rightarrow \mathrm{MnO}_{2(\mathrm{~s})}+x \mathrm{ClO}_{2(\mathrm{aq})}$$