ICSE BoardEnglish MediumSTD 9CHEMISTRYAtmospheric Pollution3 Marks
Question
State how CFC breaks the ozone layer.
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Answer
Depletion of $\mathrm{O}_3$ by CFC: CFC is broken by UV rays of sunlight to produce $[\mathrm{Cl}]$ atom or free radical $[\mathrm{Cl}]$ which is highly reactive in the atomic form and it forms $\mathrm{ClO}_{(\mathrm{g})}$ with $\mathrm{O}_2$. $\begin{aligned} & \mathrm{CFCl}_3 \xrightarrow{\mathrm{UV}(\mathrm{Sun})} \mathrm{CFCl}_2+\mathrm{Cl}(\text { atom }) \\ & \mathrm{Cl}(\mathrm{g})+\mathrm{O}_3(\mathrm{~g}) \longrightarrow \mathrm{ClO}(\mathrm{g})+\mathrm{O}_2(\mathrm{~g})\end{aligned}$ This depletes ozone. $\mathrm{ClO}$ further produces more $[\mathrm{Cl}]$ free radical and destroys more of $\mathrm{O}_3$, thereby resulting in ozone depletion. $\mathrm{ClO}(\mathrm{g})+\mathrm{O}(\mathrm{g}) \longrightarrow \mathrm{Cl}(\mathrm{g})+\mathrm{O}_2(\mathrm{~g})$
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