Which of the following is responsible for depletion of the ozone layer in the upper strata of the atmosphere :-
A
Ferrocene
B
Fullerenes
C
Freons
D
Polyhalogens
The answer is C.
Solution
Freons are chlorofluorocarbons (CFCs) such as $CCl_2F_2$ (freon-12), used in refrigerators, air conditioners and aerosol sprays. They are very stable, so they slowly diffuse unchanged into the stratosphere. There, ultraviolet radiation breaks them to give chlorine free radicals: $CF_2Cl_2 \xrightarrow{h\nu} \dot{C}l + \dot{C}F_2Cl$ $\dot{C}l + O_3 \rightarrow Cl\dot{O} + O_2$ $Cl\dot{O} + O \rightarrow \dot{C}l + O_2$ The chlorine radical is regenerated, so one radical can destroy thousands of ozone molecules. Ferrocene (an organometallic sandwich compound) and fullerenes (carbon allotropes) do not cause ozone depletion. So freons are responsible for the depletion of the ozone layer.
ConceptCFCs and ozone depletion
Haloalkanes and Haloarenes in past papers
55 questions from this chapter have appeared across 25 exam years.
