Question

Explain why an oxidizing agent undergoes reduction.

Short answer

An oxidizing agent oxidizes other element and itself gets reduced in a chemical reaction.

Electron lost by a reducing agent is gained by an oxidizing agent.

Step-by-step solution

Oxidation

Oxidation is the loss of electrons. It is also represented by increase in oxidation number. An oxidizing agent oxidizes other reactant and itself gets reduced in a chemical reaction.

Reduction

Reduction is the gain of electrons or decrease in oxidation number. A reducing agent reduces the other reactant and itself gets oxidized in a chemical reaction.

Determine oxidizing and reducing agent in redox reaction

A redox reaction can be written as:

$\mathbf{A}\mathbf{+}\mathbf{B}\mathbf{\to }{\mathbf{A}}^{\mathbf{+}}\mathbf{+}{\mathbf{B}}^{\mathbf{-}}$

Now the half reactions are:

$\begin{array}{l}\mathbf{A}\mathbf{\to }{\mathbf{A}}^{\mathbf{+}}\mathbf{+}{\mathbf{e}}^{\mathbf{-}}\\ \mathbf{B}\mathbf{+}{\mathbf{e}}^{\mathbf{-}}\mathbf{\to }{\mathbf{B}}^{\mathbf{-}}\end{array}$

Here, A is getting oxidized and its oxidation state changes from 0 to +1.

And, B is getting reduced and its oxidation state changes from 0 to -1.

Hence, B acts as an oxidizing agent. By accepting electrons, B gets reduced and oxidizes A. Electrons lost by A are gained by oxidizing agent B.