pBlock ElementsII 1 Question 14
14. Concentrated nitric acid upon long standing, turns yellow-brown due to the formation of
(2013 Main)
(a) $\mathrm{NO}$
(b) $\mathrm{NO}_{2}$
(c) $\mathrm{N}_{2} \mathrm{O}$
(d) $\mathrm{N}{2} \mathrm{O}{4}$
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Solution:
- $\mathrm{NO}{2}$ is a brown coloured gas and imparts this colour to concentrated $\mathrm{HNO}{3}$ during long standing.
$$ 4 \mathrm{HNO}{3} \longrightarrow 2 \mathrm{H}{2} \mathrm{O}+2 \mathrm{NO}{2}+3 \mathrm{O}{2} $$
