A faulty domestic gas boiler is found to release carbon monoxide ($CO$) rather than carbon dioxide ($C{O}_2$) into a home. Explain why carbon monoxide is formed in this appliance.

Liquid fuels, such as diesel, undergo hydrodesulfurisation to remove sulfur impurities before commercial distribution. Explain how this pre-combustion removal of sulfur prevents the chemical weathering of ancient limestone ($CaC{O}_3$) structures.

Although nitrogen gas ($N_2$) is highly unreactive due to its strong triple bond, significant quantities of nitrogen oxides ($N{O}_x$) are released from vehicle exhaust pipes. Explain how these oxides are formed within an internal combustion engine.