## Slowest step

$K = \frac{k_{forward}}{k_{reverse}}$

Jane Burgan 1C
Posts: 73
Joined: Fri Sep 28, 2018 12:15 am

### Slowest step

Why does the slowest step of the reaction mechanism determine the rate of the overall reaction?

WilliamNguyen_4L
Posts: 65
Joined: Fri Sep 28, 2018 12:28 am

### Re: Slowest step

In reactions the fast steps occur at such a high rate that overall they contribute almost nothing to the total time of the reaction. Although they do contribute a little we just approximate the rate to be just the slow step only. A way to think about this is if the slow step took a year and the fast step took a couple seconds then overall it's the slow step dictating the rate since a couple seconds is almost nothing compared to a year.

Posts: 60
Joined: Fri Sep 28, 2018 12:16 am

### Re: Slowest step

The fast steps, in comparison to the slow step, are negligible because they occur so quickly. The time that the slow step takes is more representative of how long the entire reaction takes.

505095793
Posts: 61
Joined: Fri Sep 28, 2018 12:25 am

### Re: Slowest step

I read an example online that helped me understand the rate determining step: The rate determining step is like a funnel in which only so much substance can pass at a time. The reaction rate is limited by the width of the "funnel", not by the amount of substance being added to the funnel. The slowest step of the reaction would be the funnel in this situation and thus would determine the rate of the reaction.

005199302
Posts: 108
Joined: Fri Sep 28, 2018 12:15 am

### Re: Slowest step

We ignore the faster, because it is negligible when considering the overall rate.