Q.Freon-12 ($\text{CCl}_2\text{F}_2$) undergoes photolysis in the stratosphere. Write the initiation step and the two propagation steps by which the chlorine radical produced destroys ozone catalytically, and give the net equation.

Initiation: high-energy stratospheric UV radiation photolyses the relatively weak $\text{C--Cl}$ bond of Freon-12, $\text{CCl}_2\text{F}_2 \xrightarrow{h\nu} {}^{\bullet}\text{CClF}_2 + \text{Cl}^{\bullet}$, releasing a reactive chlorine radical. Propagation step 1: the chlorine radical attacks an ozone molecule, $\text{Cl}^{\bullet} + \text{O}_3 \to \text{ClO}^{\bullet} + \text{O}_2$, converting ozone to ordinary oxygen and forming chlorine monoxide radical. Propagation step 2: chlorine monoxide radical reacts with a free oxygen atom (present in the stratosphere from ozone's own natural photochemical cycle), $\text{ClO}^{\bullet} + \text{O} \to \text{Cl}^{\bullet} + \text{O}_2$, which regenerates the original chlorine radical and forms more ordinary oxygen. Adding the two propagation steps gives the net transformation $\text{O}_3 + \text{O} \to 2\,\text{O}_2$; becau …

Write the two propagation steps so that the chlorine species clearly cancels out (appears as both a reactant of step 1 and a product of step 2) -- that ca …

Writing only a single step (Cl* + O3 -> ClO* + O2) and stopping there, which makes the process look like Cl is simply consumed rather …