WAEC Chemistry 2021 Paper

Concept:Acid rain is caused by acidic oxides, mainly oxides of nitrogen and sulphur, which dissolve in rainwater to form acids.Explanation:Nitrogen dioxide, $\mathrm{NO}_2$, is an acidic oxide.It reacts with water vapour and oxygen in the atmosphere to form nitric acid, $\mathrm{HNO}_3$.This nitric acid makes the rain acidic and causes acid rain.Carbon monoxide, $\mathrm{CO}$, is neutral and does not form acid rain.Nitrogen monoxide, $\mathrm{NO}$, can form acid rain eventually, but $\mathrm{NO}_2$ is the more direct and common nitrogen oxide responsible.Hydrogen peroxide, $\mathrm{H}_2\mathrm{O}_2$, is not an oxide of a non-metal that forms acid rain in the same way.Answer:$\mathrm{NO}_2$ (Option D) causes acid rain.