Question

During a thunderstorm, rain water contains nitric acid. Explain with reaction.

Answer 1

The nitrogen present in the atmosphere reacts with oxygen to form nitric oxide during lightning.

$\underset{\mathrm{nitrogen}}{\underset{}{{\mathrm{N}}_2\left(\mathrm{g}\right)}}+\underset{\mathrm{oxygen}}{\underset{}{{\mathrm{O}}_2\left(\mathrm{g}\right)}}\rightleftharpoons \underset{\mathrm{nitric}\mathrm{oxide}}{\underset{}{2\mathrm{NO}\left(\mathrm{g}\right)}}$

Then the nitric oxide is further oxidised to nitrogen dioxide.

$\underset{\mathrm{nitric}\mathrm{oxide}}{\underset{}{2\mathrm{NO}\left(\mathrm{g}\right)}}+\underset{\mathrm{oxygen}}{\underset{}{{\mathrm{O}}_2\left(\mathrm{g}\right)}}\rightleftharpoons \underset{\mathrm{nitrogen}\mathrm{dioxide}}{\underset{}{2{\mathrm{NO}}_2\left(\mathrm{g}\right)}}$

In the atmosphere the nitrogen dioxide dissolves in presence of oxygen and forms nitric acid which is washed down by rain combines with salt on the surface of the earth.

$\underset{\mathrm{nitrogen}\mathrm{dioxide}}{\underset{}{4{\mathrm{NO}}_2\left(\mathrm{g}\right)}}+\underset{\mathrm{rain}\mathrm{water}}{\underset{}{2{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)}}+\underset{\mathrm{oxygen}}{\underset{}{{\mathrm{O}}_2\left(\mathrm{g}\right)}}\to \underset{\mathrm{nitric}\mathrm{acid}}{\underset{}{4{\mathrm{HNO}}_3\left(\mathrm{g}\right)}}$