The chemical composition of acid rain is: H2O (l) + H2CO3 (aq) HCO3− (aq) + H3O+ (aq) per Wikipedia, CO2+H2O yields H2CO3(1) H2CO3 yields H+ + HCO3-(2) per answers.yahoo.com
Some pollutants that cause acid rain are sulfur and nitrogen.
Acid rain is caused by emissions of nitrogen oxides carbon dioxide and sulfur dioxide which react with the water in the atmosphere to produce Acid Rain.