Question

The brownish yellow colour of nitric acid is removed by :

• A. bubbling air through warm acid
• B. bubbling acid
• C. passing ammonia through acid
• D. adding little $Mg$ powder

Answer 1

The correct option is A bubbling air through warm acid

Nitric acid obtained in the laboratory is slightly yellow due to the dissolution of nitrogen dioxide which is produced due to thermal decomposition.

$4HN{O}_3⟶2H_{2}O+4N{O}_2+O_2$

If $C{O}_2$ is bubbled through the acid, it turns colourless- because it drives out $N{O}_2$ from warm acid which is further oxidized to nitric acid.

Hence, option A is correct.