Describe how sulfur dioxide causes acid rain.

Sulfur dioxide is a gas which reacts with oxygen to form another gas called sulfur trioxide. When this rises up into the atmosphere and dissolves in water droplets sulphuric acid is formed so that when it rains, acid rain is produced.

Acid rain or acid deposition is a broad term that includes any form of precipitation with acidic components, such as sulfuric or nitric acid that fall to the ground from the atmosphere in wet or dry forms. This can include rain, snow, fog, hail or even dust that is acidic.

Acid rain results when emissions of SO2 and NOx are released into the atmosphere and transported by wind and air currents. The SO2 and NOx react with water (H2O), (O2) and other chemicals to form sulfuric and nitric acids. These then mix with water and other materials before falling to the ground.

Sulfur dioxide dissolves in rainwater to form sulfurous acid (relevant chemical equation can be seen from attached picture) which makes the rainwater acidic.

When sulphur dioxide combines with water and air present in the atmosphere, it forms sulphuric acid which is the main component for the acid rain.