Question

A single chlorine mplecule can deplete______ molecules of ozone

• A. $10,000$
• B. $10,00,000$
• C. $50,000$
• D. $1,00,000$

Answer 1

Answer: (D)

Among the $ODSs$ (Ozone depleting substances), $CFCs$ or chlorofluorocarbons have the most damaging effect as they produce active chlorine ($CIO$ and $Cl$ radicals) in presence of $UV$ radiation, which initiates a chain reaction of ozone destruction. One molecule of active chlorine can destroy nearly, $1,00,000$ molecules of ozone.
$\mathrm{CFCs}\stackrel{\text{ UV rays}}{\to }\mathrm{Cl}$
$\mathrm{Cl}+\mathrm{O}{}_3\to \mathrm{O}{}_2+\mathrm{ClO}$
$\mathrm{ClO}+\mathrm{O}{}_3\to \mathrm{Cl}+2\mathrm{O}{}_2$
The ozone depletion by active chlorine is a catalytic reaction cycle i.e., the molecule that started the reaction is reformed to continue the process. Because of catalytic reactions, an individual chlorine atom can destroy multiple ozone molecules before it is converted into a form harmless to ozone.