When healthy, earth's stratosphere contains a low concentration of ozone (O3) that absorbs potential — Qualitative and Quantitative Analysis Chemistry Question

Question

When healthy, earth's stratosphere contains a low concentration of ozone (O3) that absorbs potentially harmful ultraviolet (UV) radiations by the cycle shown below: O3 --(hv)--> O2 + O O2 + O --(Heat)--> O3 chlorofluoro carbon refrigerants, such as freon 12 (CF2Cl2), are stable in lower atmosphere, but in the stratosphere, they absorb high energy UV radiation to generate chlorine radicals. CF2Cl2 --hv--> CF2Cl• + Cl• The presence of small number of chlorine radicals appears to lower ozone concentrations dramatically. The following reactions are all known to be exothermic (except the one requiring light) and to have high rate constant. A : Cl—O—O—Cl --hv--> O2 + 2Cl• B : Cl—O• + O -> O2 + Cl• C : Cl• + O3 -> Cl—O• + O2 D : 2Cl—O• -> Cl—O—O—Cl