One of the winners of the 1995 Nobel Prize in Chemistry was Paul J. Crutzen, who showed that emissions of nitrogen oxides from jet airplanes could contribute to the destruction of the ozone layer.

Using chemical equations, outline a mechanism by which nitrogen oxides are able to deplete ozone.

\({\text{N}}{{\text{O}}_2} + {\text{hf}} \to {\text{NO}} + {\text{O}} \bullet \);

\({\text{NO}} + {{\text{O}}_3} \to {\text{N}}{{\text{O}}_2} + {{\text{O}}_2}\);

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

\({\text{O}} \bullet  + {{\text{O}}_3} \to {\text{2}}{{\text{O}}_2}\);

No penalty for missing the free radical sign or using them on nitrogen oxides.

Accept other symbols in place of hf e.g. uv, h or light, in front of or above the arrow.

Many correct answers were seen for the outline of mechanism by which nitrogen oxides are able to deplete ozone, though rarely achieving full marks.