Explain, on a molecular level, why ozone dissociates with radiation of a longer wavelength than oxygen.

Nitrogen(II) oxide, NO, is a primary pollutant that depletes the ozone layer. State two equations that show how this oxide catalyses the depletion of ozone in the stratosphere.

\({{\text{O}}_{\text{3}}}\) needs less energy/has weaker bonding/has lower bond enthalpy;

Accept converse argument for \({O_2}\).

\({{\text{O}}_{\text{3}}}\) has bond order 1.5/intermediate between double and single and \({{\text{O}}_{\text{2}}}\) has bond order 2/double bond;

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

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

Accept “\(N{O_2} \bullet (g) + {O_3}(g) \to NO \bullet (g) + 2{O_2}(g)\)” for M2.

Accept NO, \(N{O_2}\) and O for radicals without \( \bullet \) if used consistently.

Accept equations with NO and \(N{O_2}\) written without \( \bullet \) but with \(O \bullet \) written.

Ignore state symbols.

Part (a) was very well done and it was nice to see reference to and discussion of bond order in many of the answers seen on scripts. In (b), few were able to give two correct equations. Inconsistency of the representation of radicals was seen on some scripts.

Part (a) was very well done and it was nice to see reference to and discussion of bond order in many of the answers seen on scripts. In (b), few were able to give two correct equations. Inconsistency of the representation of radicals was seen on some scripts.