Question

34. Acid formed as a result of lightening reaches the earth's surface through precipitation, thus contributing to the acid rain as well as to the growth of plants. Justify.

Answer 1

• The gases like Nitrogen dioxide $\left({\mathrm{NO}}_2\right)$ and Sulphur dioxide $\left({\mathrm{SO}}_2\right)$ that are released from factories, burning of fossil fuels, etc. dissolve in rainwater and form Nitric acid $\left({\mathrm{HNO}}_3\right)$ and Sulphuric acid $\left({\mathrm{H}}_2{\mathrm{SO}}_4\right)$. This rain when reaches in earth's surface is called acid rain.
• Nitric acid which is formed as a result of the lightning process is very dilute in nature.
• When comes to ground in acid rain, it reacts with metal carbonates such as Calcium carbonate or Limestone $\left({\mathrm{CaCO}}_3\right)$.
• The reaction involved is: $\underset{\mathrm{Calcium}\mathrm{carbonate}}{{\mathrm{CaCO}}_3}+\underset{\mathrm{Nitric}\mathrm{acid}}{2{\mathrm{HNO}}_3}\to \underset{\mathrm{Calcium}\mathrm{nitrate}}{\mathrm{Ca}{\left({\mathrm{NO}}_3\right)}_2}+\underset{\mathrm{Carbon}\mathrm{dioxide}}{{\mathrm{CO}}_2}+\underset{\mathrm{Water}}{{\mathrm{H}}_2\mathrm{O}}$
• The Calcium nitrate formed in the above reaction helps in the growth of the plants.