JEE Main 2014 — Environmental Chemistry Question with Solution

Freons and chlorofluorocarbon find their way to stratosphere through without being destroyed in the troposphere due to their low reactivity. In the stratosphere the $\mathrm{Cl}$ and $\mathrm{Br}$ atoms are liberated from the parent compounds by the action of ultraviolet light e.g. $$\begin{array}{rl}& {\mathrm{CF}}_2{\mathrm{Cl}}_2+hv⟶{\mathrm{CF}}_2\mathrm{Cl}+\mathrm{Cl}\\ & {\mathrm{CFCl}}_3+hv⟶{\mathrm{CFCl}}_2+\mathrm{Cl}\end{array}$$ The $\mathrm{Cl}$ atoms can destroy ozone molecules through a variety of catalytic cycles.