Question

$H_2{O}_2$ is used as

• A. An oxidant only
• B. A reductant only
• C. An acid only
• D. An oxidant, a reductant and an acid

Answer 1

The correct option is

D

An oxidant, a reductant and an acid

Hydrogen peroxide behaves as an oxidising as well as reducing agent in both acidic and

basic solution. The oxidation state of oxygen in hydrogen peroxide is -1 .It can be oxidised

to oxygen or reduced to water or hydroxide ion.

Hydrogen peroxide is a powerful oxidising agent but a weak reducing agent.

Oxidising character

Hydrogen peroxide act as an oxidising agent both in acidic as well as alkaline medium .

As an oxidant:

$2F{e}^{2+}\left(aq\right)+H_2{O}_2+2H^{+}\left(aq\right)⟶2F{e}^{3+}\left(aq\right)+2H_{2}O\left(l\right)$

Reducing character

In presence of strong oxidising agent, hydrogen peroxide behave as a reducing agent in

acidic as well as alkaline medium.In these reactions, molecular oxygen is always produced by the combination of H2O2H_2O_2H2​O2​ with the oxygen atom released by the strong oxidising agent

As as reductant (these reactions are apt to produce $O_2$ in lab):

$NaOCl+H_2{O}_2⟶O_2+NaCl+H_{2}O$

$2KMn{O}_4+3H_2{O}_2⟶2Mn{O}_2+2KOH+2H_{2}O+3O_2$

Acidic nature

Pure hydrogen peroxide turns blue litmus red but its dilute solution is neutral to litmus. It

thus behaves as a weak acid. Its dissociation constant is 1.55 × ${10}^{-12}$ at which at 298 K

which is only slightly higher than that of water.

Hydrogen peroxide is only a slightly stronger acid than water. Since hydrogen peroxide has two ionizable hydrogen atoms, it forms two series of salts i.e. hydroperoxides and peroxides.

The acidic nature of hydrogen peroxide is shown by its neutralization reaction with

Hydroxides.

$NaOH+H_2{O}_2⟶NaH{O}_2+H_{2}O$

$2NaOH+H_2{O}_2⟶N{a}_2{O}_2+2H_{2}O$