Depletion of ozone occurs as;
$2{\mathrm{O}}_3⟶3{\mathrm{O}}_2$
Step1 : ${\mathrm{O}}_3\stackrel{{\mathrm{K}}_{\mathrm{c}}}{\rightleftharpoons }{\mathrm{O}}_2+\left(\mathrm{O}\right)$ (fast)
Step2 : ${\mathrm{O}}_3+\left(\mathrm{O}\right)\stackrel{{\mathrm{K}}_{\mathrm{c}}}{\rightleftharpoons }2{\mathrm{O}}_2$ (slow)
What is the order of the reaction?

.

The slow step is rate-determining step.

Rate=k′[O₃​][O]-----------------1

Now K= $\frac{\left[{\mathrm{O}}_2\right]\left[\mathrm{O}\right]}{\left[{\mathrm{O}}_3\right]}$
[O] =$\frac{\mathrm{K}\left[{\mathrm{O}}_3\right]}{\left[{\mathrm{O}}_2\right]}$

Substitute value of [O] in equation 1

Rate=${\mathrm{K}}^{\text{'}}\mathrm{K} {\left[{\mathrm{O}}_3\right]}^2{\left[{\mathrm{O}}_2\right]}^{-1}$

overall order =2−1=1