Question

he decomposition of ozone in the upper atmosphere is facilitated by NO. The overall reaction and the rate law are O3(g)+O(g)→2O2(g) Rate=k[O3][NO] Write a mechanism that is consistent with the rate law.

Answer 1

rate law involves O3 and NO, therefore perhaps the first step is a bimolecular reaction of these two.
step 1: O3 + NO --> O2 + NO2 (slow step)
O2 is one of the products, therefore why not try that as one of the products of the first reaction. The other oxygen from ozone can stick to nitric oxide to form nitrogen dioxide.
In step two, you will need to use up the NO2 (it does not appear as a product in the reaction) and you will need to make another O2. However, we have not yet used our other reactant (O).
step 2: O + NO2 --> O2 + NO
NO appears, now, on both sides of the reaction. It will cancel out when you add both of the elementary steps. NO2 also appears on both sides and will also cancel out. The remainder of the reactants and products left actually participate in the overall reaction as written. Forgot to mention: the first elementary step is the rate determining step. this is where you get the rate law.

R = k [O3] [NO]