Answer
The slow step of a reaction is the rate-determining step.
Work Step by Step
The slow step of a reaction is the rate determining step. This means:
If the reaction occurs like:
Slow step: NO2 + F2 ---> NO2F + F
Fast Step: F + NO2 ---> NO2F
Over all reaction 2NO2 + F2 ---> 2NO2F
So for the above reaction althought the second step is fast the reaction becomes slow because of the first step. As a result the first step is a rate determining step.
