The Rate-Determining Step for a Multistep Mechanism

As with the reaction in Sample Exercise 14.13, most reactions occur by mechanisms that involve two or more elementary reactions. Each step of the mechanism has its own rate constant and activation energy. Often one step is much slower than the others, and the overall rate of a reaction cannot exceed the rate of the slowest elementary step. Because the slow step limits the overall reaction rate, it is called the rate-determining step (or rate-limiting step). 

Step 1 Point 1 Point 2 (through toll plaza A) 

Step 2 Point 2 Point 3 (through toll plaza B) 

Overall Point 1 Point 3 (through both toll plazas) 

For which of the two scenarios in the figure will one get from point 1 to point 3 most rapidly  

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