Nitrogen dioxide is formed in a two-stage process. Describe one anthropogenic (man-made) source of nitrogen dioxide and state the two chemical equations for its formation.

Both of these air pollutants also contribute to acid deposition. State one chemical equation for each gas to describe how each forms an acidic solution.

combustion of fuels (at high temperature);

Accept internal combustion/aircraft/jet engines.

\({{\text{N}}_2} + {{\text{O}}_2} \to {\text{2NO}}\) and \(2{\text{NO}} + {{\text{O}}_2} \to {\text{2N}}{{\text{O}}_2}\);

\({\text{2N}}{{\text{O}}_2} + {{\text{H}}_2}{\text{O}} \to {\text{HN}}{{\text{O}}_2} + {\text{HN}}{{\text{O}}_3}/{\text{4N}}{{\text{O}}_2} + {\text{2}}{{\text{H}}_2}{\text{O}} + {{\text{O}}_2} \to {\text{4HN}}{{\text{O}}_3}\);

\({\text{S}}{{\text{O}}_2} + {{\text{H}}_2}{\text{O}} \to {{\text{H}}_2}{\text{S}}{{\text{O}}_3}/{\text{2S}}{{\text{O}}_2} + {\text{2}}{{\text{H}}_2}{\text{O}} + {{\text{O}}_2} \to {\text{2}}{{\text{H}}_2}{\text{S}}{{\text{O}}_4}\);

The man-made source of nitrogen oxide was generally very well answered, although the equations for its formation proved demanding.

The chemical equation for the formation of sulfuric acid was given correctly by many candidates, but it was surprising to see that a significant number of candidates did not know the chemical formula for nitric acid.