Which of the following reactions is primarily responsible for the depletion of the ozone layer in the stratosphere by chlorofluorocarbons?

Solution

1. CFCs undergo photolysis in the stratosphere to release chlorine radicals ${\text{Cl}}^{\bullet }$.
2. The chlorine radical reacts with ozone to form chlorine monoxide ${\text{ClO}}^{\bullet }$ and oxygen.
3. The ${\text{ClO}}^{\bullet }$ radical then reacts with atomic oxygen $\text{O}$ to regenerate the ${\text{Cl}}^{\bullet }$ radical.
4. The net reaction is ${\text{O}}_3+\text{O}\to 2{\text{O}}_2$, which depletes the ozone layer.
5. Hence the answer is (B).