Question

When nitric acid is exposed to light,nitrogen changes its oxidation state from:

• A. $+5$ to $+3$
• B. $+4$ to $+3$
• C. $+5$ to $+4$
• D. $+4$ to $+2$

Answer 1

Answer: (C)

$+5$ to $+4$

Nitric acid is subject to thermal or light decomposition and for this reason it was often stored in brown glass bottles:

$4HN{O}_3\to 2H_{2}O+4N{O}_2+O_2$

Here,oxidation state of $N$ changes from $+5$ to $+4$.