Question

State a reaction in which ${\mathrm{SO}}_2$ acts as an oxidizing agent.

Answer 1

1. Oxidizing agent: A substance that gains hydrogen or loses oxygen during a reaction is said to be reduced and is characterized as an oxidizing agent.
2. Reducing agent: A substance that gains oxygen or loses hydrogen during a reaction is oxidized, called a reducing agent.
3. When Hydrogen Sulphide $\left({\mathrm{H}}_2\mathrm{S}\right)$ reacts with Sulphur Dioxide$\left({\mathrm{SO}}_2\right)$, it forms water and elemental sulfur.
4. $$\begin{gathered} \mathrm{Reaction}:2H_{2}S\mathit{\left(}g\mathit{\right)}\mathit{}+S{O}_2\mathit{\left(}g\mathit{\right)}\mathit{}\mathit{}\mathit{}\mathit{}\mathit{}\to 2H_{2}O\left(l\right)\mathit{}+3S\left(s\right) \\ \mathit{}\mathit{}\mathit{}\mathit{}\mathit{}\mathit{}\mathit{}Hydrogen\mathit{}Sulfide\mathit{}\mathit{}\mathit{}\mathit{}\mathit{}Sulfur\mathit{}dioxide\mathit{}\mathit{}\mathit{}\mathit{}\mathit{}\mathit{}Water\mathit{}\mathit{}\mathit{}\mathit{}\mathit{}\mathit{}\mathit{}\mathit{}\mathit{}Sulfur \end{gathered}$$
5. Here ${\mathrm{H}}_2\mathrm{S}$ is oxidized to ${\mathrm{H}}_2\mathrm{O}$ and ${\mathrm{SO}}_2$ is reduced to $\mathrm{S}$.
6. Because ${\mathrm{SO}}_2$ loses oxygen to form $\mathrm{S}$, it is being reduced and hence it can be referred to as an oxidizing agent.