Step 1. NO2(g)+NO2(g)NO3(g)+NO(g) (slow) Step 2. NO3(g)+CO(g)NO2(g)+CO2(g) (fast) fter writing out the overall (or net equation), NO3 is excluded because it is a(n) while one molecule of NO2 is excluded because it is a(n) The molecularity of Step 1 is while the molecularity of Step 2 is The rate-determining step of this mechanism is because it is the step. With this knowledge, the rate law for the overall (or net) reaction can be written; the reaction is order in NO2 and order in CO which means it is order overall