## Overall rate law

$aR \to bP, Rate = -\frac{1}{a} \frac{d[R]}{dt} = \frac{1}{b}\frac{d[P]}{dt}$

Petrina Kan 2I
Posts: 102
Joined: Fri Aug 30, 2019 12:17 am

### Overall rate law

I am confused as to why the overall rate law is the rate law of just the slowest step. I understand why the slow step must determine the rest of it, but why are the species in the other steps not included in the overall rate law?

Kevin Xu 4F
Posts: 50
Joined: Fri Aug 09, 2019 12:16 am

### Re: Overall rate law

I think this is because this is a very simplified model and way of looking at reactions. Here, we assume an all or nothing approach to reaction processes where the reaction either proceeds to completion or does not proceed at all. This is a result of the activation energies of the reaction, and the slowest step determines if the reaction proceeds because it has the highest activation energy. As a result of this factor, the reaction mechanisms are thus dictated and simplified to only the slowest step.

305385703
Posts: 102
Joined: Thu Jul 11, 2019 12:15 am

### Re: Overall rate law

Since this step is the slowest, then the rate of the entire reaction depends on it. Thus, only the concentrations of this reaction intermediate contribute to the overall reaction rate.

Elizabeth Harty 1A
Posts: 125
Joined: Sat Jul 20, 2019 12:16 am

### Re: Overall rate law

I think its because the entire reaction depends on the slowest step.

Maria Poblete 2C
Posts: 102
Joined: Wed Sep 18, 2019 12:15 am

### Re: Overall rate law

Like someone said before, it's essentially an all or nothing kind of behavior. Someone explained it to me in a helpful analogy: if you're hiking with a group of people, the slowest person in the group determines the pace of their hike. The other people, no matter how fast they are, must keep the pace of the slowest person in order to stick together as a group. Hope this helps!

805422680
Posts: 103
Joined: Sat Sep 14, 2019 12:16 am

### Re: Overall rate law

The slow step is considered the rate determining step. That means that the rate of the entire reaction is determined by that step. Imagine you are walking up a hill as a group, the slowest member of the group is the rate determining step

Naneeta Desar 1K
Posts: 106
Joined: Fri Aug 09, 2019 12:15 am

### Re: Overall rate law

The whole reaction depends on the slow step.

Nawal Dandachi 1G
Posts: 102
Joined: Sat Sep 28, 2019 12:16 am

### Re: Overall rate law

Because it is the slowest reaction, it is the "rate determining step" and the overall reaction would depend on it.

Matt Sanruk 2H
Posts: 131
Joined: Wed Sep 18, 2019 12:21 am

### Re: Overall rate law

Since its the slowest step, this step is going to be the one that is the most prominent in determining the overall rate since the rate is at this slow rate most of the time.