OPSC 2016 Solved Paper

Acid rain results when sulphur dioxide $\left({\mathit{S}\mathit{O}}_2\right)$ and nitrogen oxides $\left({\mathit{N}\mathit{O}}_{\mathit{x}}\right)$ are emitted into the atmosphere and transported by wind and air currents. The ${\mathit{S}\mathit{O}}_2$ and ${\mathit{N}\mathit{O}}_{\mathit{x}}$ react with water, oxygen and other chemicals to form sulphuric and nitric acids. These then mix with water and other materials before falling to the ground. While a small portion of the ${\mathit{S}\mathit{O}}_2$ and ${\mathit{N}\mathit{O}}_{\mathit{x}}$ that cause acid rain is from natural sources such as volcanoes, most of it comes from the burning of fossil fuels.