Question

Pure nitric acid is unstable to heat or sunlight.

• A. True
• B. False

Answer 1

The correct option is A

True

Pure nitric acid is unstable to heat or sunlight. It decomposes to give yellow solution due to the formation of nitrogen dioxide. Thus, 100% nitric acid is not generally used.

$4HN{O}_3\underset{Sunlight}{\overset{\Delta }{\to }}4N{O}_2+2H_2+O_2$

In the presence of sunlight, nitric acid decomposes even at room temperature. The nitric acid stored in a bottle turns yellow. This colour is due to dissolved $N{O}_2$ in $HN{O}_3$. To avoid the decomposition, nitric acid is normally stored in coloured bottles.