Many fossil fuels contain sulfur impurities. When these fuels are burned, the sulfur is oxidised to form sulfur dioxide.
S(s) + O2(g) → SO2(g)
This sulfur dioxide then dissolves in droplets of rainwater to form sulfurous acid.
SO2(g) + H2O(l) → H2SO3(aq)
Acid rain reacts with metals and rocks such as limestone. Buildings and statues are damaged as a result.
Acid rain damages the waxy layer on the leaves of trees and makes it more difficult for trees to absorb the minerals they need for healthy growth. They may die as a result.
Acid rain also makes rivers and lakes too acidic for some aquatic life to survive.