While explaining the recent developing ozone hole on Antarctica, teacher makes a remark that 'without ozone layer, organisms cannot survive on Earth'. Kalpana gets curious about the various aspects of ozone layer and asks some questions to her teacher.
What has led to its depletion?
The ozone layer is reduced when man-made CFC molecules (comprised of chlorine, fluorine, and carbon) reach the stratosphere and are broken apart by UV energy from the sun.
These substances that lower the ozone layer do not directly destroy ozone. First they undergo photolysis, forming hydrogen chloride (HCl) or chlorine nitrate (ClONO2), molecules that do not react with ozone directly, but slowly decompose, giving, among other things, a small number of chlorine atoms (Cl) and Of chlorine monoxide (ClO) molecules that catalyze the destruction of ozone.
The reactions involved in the processes of destruction are more than 100, but can be simplified in the following:
Cl + O3→ ClO + O2
ClO + O → Cl + O2
Net effect: O3 + O → 2 O2
The chlorine atom acts as a catalyst, ie it is not consumed in the reaction, so it destroys thousands of ozone molecules before disappearing.