Describe, by means of equations, how nitrogen(II) oxide, NO, catalyses the depletion of ozone.

Identify and state the source of one other ozone-depleting pollutant.

\({\text{NO(g)}} + {{\text{O}}_{\text{3}}}{\text{(g)}} \to {\text{N}}{{\text{O}}_{\text{2}}}{\text{(g)}} + {{\text{O}}_{\text{2}}}{\text{(g)}}\);

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

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

\({\text{N}}{{\text{O}}_2}{\text{(g)}} + {{\text{O}}_3}{\text{(g)}} \to {\text{NO(g)}} + {\text{2}}{{\text{O}}_2}{\text{(g)}}\);

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

Accept representation of radicals without \( \bullet \) if consistent throughout.

Ignore state symbols.

chlorofluorocarbons/CFCs and

propellants in aerosol sprays/cans / (old) refrigerators / air conditioners / solvents / foaming agents/plastic foams / fire extinguishers;

Accept specific examples (eg, Freon/dichlorodifluoromethane/\(C{F_2}C{l_2}\) etc).

The relative strength of the bonds in oxygen and ozone was well known, along with the link between this and the frequency of radiation absorbed. Students were also very familiar with the sources of CFCs and the role of these in ozone depletion. The equations involved with the catalysis of ozone depletion by nitrogen(II) oxide were however a significantly greater challenge.

The relative strength of the bonds in oxygen and ozone was well known, along with the link between this and the frequency of radiation absorbed. Students were also very familiar with the sources of CFCs and the role of these in ozone depletion. The equations involved with the catalysis of ozone depletion by nitrogen(II) oxide were however a significantly greater challenge.