The Theme of Acid Rain in Chemical Reactions
Robert Angus Smith, an English chemist and climatologist, first coined the phrase "acid rain" in 1852.3 He used the phrase to describe the acidic precipitation that fell over major cities in England at the start of the Industrial Revolution.
Neutral water has a pH of 7. Rainfall can become naturally acidified from dissolved carbon dioxide that is a normal everyday component of the atmosphere. How does this raise the pH? The carbon dioxide reacts with water to form a weak acid called carbonic acid.
CO2 (g) + H2O (l) ←→ H2CO3 (aq)
H2CO3 (aq) + H2O (l) ←→ H3O+ + HCO3- (aq)
NO2, SO2, and SO3 can also react with water in the atmosphere to produce acids. Water droplets carrying these acids can then precipitate as rain or snow—thus the term acid rain.
Industrial factories pumped a lot of CO2 into the atmosphere during the Industrial Revolution. Mr. Smith noticed more acidic rainfall at this time.
Acid rain is a problem because it can fall on environments that cannot tolerate such acidity. This can have serious effects. These problems can result in the death of fish and other life forms in lakes and ponds, dead or dying trees in forests, and buildings that crumble way before their time. Check out the forest below which has been destroyed by toxic acid rain. If acid rain can do that much damage to trees, imagine the effect it can have on fish, humans, and other wildlife. Yikes.
Trees destroyed by acid rain. (Image from here.)
The ultimate resolution to the acid rain problem is to have a major crackdown on industries that produce oxides and CO2. A lot of money and time is going into valuable research to solve these huge environmental problems.