Question

How does air pollution lead to acid rain?

Answer 1

Some factories and industries burn sulphur to release sulphur dioxide into the air. For example, during preparation for the contact process.
`S+O_2->SO_2`
This sulphur dioxide then reacts with oxygen in the air to form sulphur trioxide.
`2SO_2+O_2->2SO_3`
(During the contact process, which is the industrial preparation of sulphuric acid, this takes place at high temperature and pressure and in the presence of a Vanadium pentoxide catalyst.).

Both of these products can react with water in the atmosphere when it rains to form acid rain, sulphurous acid or sulphuric acid.

`SO_2+H_2O->H_2SO_3`

`SO_3+H_2O->H_2SO_4`

This acid rain can erode away metals etc.