Question

On the basis of chemical reactions involved, explain how do chlorofluorocarbons cause thinning of ozone layer in stratosphere.

Answer 1

In the stratosphere, chlorofluorocarbons get broken down by powerful UV radiations, releasing chlorine free radical. This can be shown as-

\[\ce{CF2Cl2 -> CF2Cl + \overset{\bullet}{C}l}\]

This chlorine radical then reacts with stratospheric ozone to form chlorine monoxide radicals and molecular oxygen. The reaction involved is-

\[\ce{\overset{\bullet}{C}l + O3 -> Cl\overset{\bullet}{O} + O2}\]

Reaction of chlorine monoxide radical with atomic oxygen produces more chlorine radicals and can be shown as-

\[\ce{Cl\overset{\bullet}{O} + [O] -> \overset{\bullet}{C}l + O2}\]

This shows that chlorine radicals are continuously regenerated and cause the breakdown of ozone. Hence, CFCs are transporting agents for continuously generating chlorine radicals into the stratosphere and damaging the ozone layer.