Final answer:
The best rate law for the overall reaction in a multistep process depends on the rate-determining step. If an intermediate is in the rate law, use previous equilibria to express it in terms of reactant concentrations. The rate law could show second-order dependence on a reactant if it is part of the rate-determining step.
Step-by-step explanation:
When considering the best rate law for the overall reaction in a multistep process, it is crucial to look at the mechanisms involved. Typically, the rate-determining step, which is the slowest step in the mechanism, dictates the rate law for the entire reaction.
If step 2 is identified as the rate-determining step, then the rate law must reflect this step. However, if the rate law includes the concentration of an intermediate species, such as [NOC1₂], we must use the equilibrium of the first step to express this intermediate concentration in terms of the starting reactant concentrations.
The final rate law should reflect a second-order dependence on the NO2 concentration if the rate-determining step involves this species. In situations where a catalyst is used, it is consumed and regenerated within the mechanism, thus confirming its role without changing the rate law.