Sat January 21, 2012 By: Kanwal Sandhu

please explain the mechanism of ozone depletion(by chlorofluorocarbons) step by step with reactions

Expert Reply
Sun January 22, 2012
A relatively recent concern is the depletion of ozone, O3 due to the presence of chlorine in the troposphere, and eventually their migration to the stratosphere. A major source of chlorine is Freons: CFCl3 (Freon 11), CF2Cl2 (Freon 12), C2F3Cl3 (Freon 113), C2F4Cl2 (Freon 114). Freons decompose in the troposphere. For example,CFCl3 ® CFCl2 + Cl
CF2Cl3 ® CF2Cl + Cl.
The chlorine atoms catalyze the decomposition of ozone,


Cl + O3 ® ClO + O2and ClO molecules further react with O generated due to photochemical decomposition of ozone:


O3 + h v ® O + O2,
ClO + O ® Cl + O2
O + O3 ® O2 + O2.
The net result or reaction is
2 O3 ® 3 O2
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