Chapter 12, Problem 79E

Consider this scenario and answer the following questions: Chlorine atoms resulting from decomposition of chloro?uoromethanes, such as CCI₂F₂, catalyze the decomposition of ozone in the atmosphere. One simplified mechanism for the decomposition is:

${\text{O}}_3\stackrel{\text{sunlight}}{\to }{\text{O}}_2+\text{O}$

${\text{O}}_3+\text{CI}\to {\text{O}}_2+\text{CIO}$

$\text{CIO}+\text{O}\to \text{CI}+{\text{O}}_2$

(a) Explain why chlorine atoms are catalysts in the gas-phase transformation:

$2{\text{O}}_3\to 3{\text{O}}_2$

(b) Nitric oxide is also involved in the decomposition of ozone by the mechanism:

${\text{O}}_3\stackrel{\text{sunlight}}{\to }{\text{O}}_2+\text{O}$

${\text{O}}_3+\text{NO}\to {\text{NO}}_2+{\text{O}}_2$

${\text{NO}}_2+\text{O}\to \text{NO}+{\text{O}}_2$

Is NO a catalyst for the decomposition? Explain your answer.