Question

Which of the following acts as an oxidising as well as reducing agent?

• A. $Na_{2}O$
• B. $H_{2}SO_{4}$
• C. $HNO_{3}$
• D. $HNO_{2}$

Answer 1

Answer: (D)

As in $HNO_{2}$ , $\text{N}$ is in $\text{+3}$ oxidation state, but nitrogen can have oxidation states from $- \text{3}$ to $+ 5$ , so it is in between the maximum and minimum oxidation state hence it can either get reduced or oxidized, depending on the conditions. It means it can act both as an oxidizing and a reducing agent. It can work both as oxidising as well as reducing agent.
(I) As an oxidising agent:
$HNO_{2}+2H^{+}+e^{-} \rightarrow NO+H_{2}O$
(II) As reducing agent:
$HNO_{2}+H_{2}O \rightarrow NO_{3}^{-}+3H^{+}+2e^{-}$