Explain why nitrogen gas has such a low reactivity.
Even though $\text{N}_2$ is not very reactive, oxides of nitrogen are found in the atmosphere through both natural and man-made processes.
Explain why internal combustion engines are able to produce oxides of nitrogen.
State and explain, using a suitable equation, how oxides of nitrogen from internal combustion engines can be stopped from entering the atmosphere.
State the role played by nitrogen dioxide, $\text{NO}_2$, in the formation of acid rain from oxides of sulfur. Write suitable equations to explain this role.
Suggest an equation to show how $\text{NO}_2$ may contribute directly to acid rain.
Explain how the uncontrolled use of nitrate fertilisers on land can cause a severe fall in water quality in rivers.