Question

Which one acts as both oxidizing as well as reducing agent?

• A. ${\mathrm{CH}}_2{\mathrm{O}}_2$
• B. ${\mathrm{HNO}}_2$
• C. ${\mathrm{KNO}}_3$
• D. ${\mathrm{O}}_2$

Answer 1

The correct option is B

${\mathrm{HNO}}_2$

Explanation for correct option

(B) ${\mathbf{HNO}}_{\mathbf{2}}$

Oxidizing and reducing agent

• A substance that causes oxidation by receiving electrons and reducing itself is said to be an oxidizing agent.
• A substance that causes reduction by giving up electrons and oxidizing itself is said to be a reducing agent.

${\mathbf{HNO}}_{\mathbf{2}}$

• The nitrogen oxidation number in ${\mathrm{HNO}}_2$ (Nitrous acid) is $+3$.
• The nitrogen atom has the ability to either gain or lose electrons when reacting with other compounds.
• It acts as both oxidizing and reducing agent.

Explanation for incorrect options

(A) ${\mathbf{CH}}_{\mathbf{2}}{\mathbf{O}}_{\mathbf{2}}$

• ${\mathrm{CH}}_2{\mathrm{O}}_2$ (Formic acid) acts as a reducing agent.
• It is easily oxidized to carbon dioxide.

(C) ${\mathbf{KNO}}_{\mathbf{3}}$

• The reduction of ${\mathrm{KNO}}_3$ (potassium nitrate) produces ${\mathrm{KNO}}_2$ (potassium nitrite).
• It acts as a reducing agent and produces ${\mathrm{HNO}}_2$ (nitrous acid) when it combines with cold, dilute mineral acids.

(D) ${\mathbf{O}}_{\mathbf{2}}$

• Oxygen is make hydrogen lose electrons.
• ${\mathrm{O}}_2$ is an oxidizing agent.

Therefore, the correct option is (B) ${\mathbf{HNO}}_{\mathbf{2}}$.