Question

Explain why and how chlorofluorocarbons are responsible for the depletion of the ozone layer?

Answer 1

Chlorofluorocarbons (CFCs) are highly stable compounds that do not degrade in the lower atmosphere. Consequently, they reach the stratosphere unchanged, where they damage the ozone layer through the following steps:

1. UV Cleavage: In the stratosphere, strong ultraviolet (UV) radiation breaks down CFC molecules, releasing highly reactive free chlorine radicals \[\ce{(Cl^{\bullet})}\].

\[\ce{CF2Cl2 ->[UV] CF2Cl + Cl^{\bullet}}\]

2. Ozone Destruction: The reactive chlorine radical attacks the ozone (O₃) molecule, breaking it down into molecular oxygen (O₂) and forming chlorine monoxide (ClO).

\[\ce{Cl^{\bullet} + O3 -> ClO + O2}\]

3. Catalytic Cycle: The ClO molecule then reacts with free oxygen atoms present in the atmosphere to regenerate the original chlorine radical \[\ce{(Cl^{\bullet})}\].

\[\ce{ClO + O -> Cl^{\bullet} + O2}\]