- Various industrial gases like carbon dioxide, sulphur dioxide, sulphur trioxide, nitric oxide, nitrogen dioxide in reaction with water of the atmosphere form acids.
- Those acids get mixed with rain and fall down in the form of rain, which is called acid rain.
- Thus, the rain containing small amount of acids formed from gases like oxides of sulphur and nitrogen etc. present in the atmosphere is called acid rain.
- The process of formation of acid rains in atmosphere occurs as follows:
Formation of sulphuric acid (H2SO4)
- SO2 + O2 ——-> H2SO3
- SO3 + H2O —–> H2SO4
Formation of Nitric acid (HNO3)
- NO + O3 —-> NO2+ O2
- 4NO2 + O2 —> N2O5
- N2O5 + H2O —-> HNO3
Formation of Hydrocholoric acid (HCl)
- Cl2 —> Cl+ Cl (chlorine free radicals)
- H2O —> H+ + OH–
- H+ + Cl– —> HCl
Formation of carbonic acid (H2CO3)
- H2O + CO2 —> H2CO3
- The acids like H2SO4, HNO3, HCl, H2CO3 get mixed with rain water and fall down on the earth in the form of acid rain.
Effects of acid rain:
- Acid rain corrodes historical monuments like statue, sculptures of metals, marble stones etc.
- It increases the acidity of soil and reduces the production of crops.
- It also increases the acidity of water resources and may hamper aquatic life (aquatic plants and animals).
- It causes different types of skin and respiratory tract diseases in human beings and other animals.
- Acid rain damages a lot of crop plants and trees in the forest each year.