Which compound acts as an oxidising as well as reducing agent

Which compound acts as an oxidising as well as reducing agent
  1. $\mathrm{SO}_{2}$
  2. $\mathrm{H}_{2} \mathrm{SO}_{4}$
  3. $\mathrm{Al}_{2} \mathrm{O}_{3}$
  4. $\mathrm{K}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7}$

Solution

The minimum and maximum oxidation number of $\mathrm{S}$ are $-2$ and $+6$ respectively. Since the oxidation number of $\mathrm{S}$ in $\mathrm{SO}_{2}$ is $+4$, therefore it can be either increased or decreased. Therefore $\mathrm{SO}_{2}$ behaves both as an oxidising as well as reducing agent.

Asked in: JEE-TOPICTESTS-CHEMISTRY

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