Slow Step

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

ian_haliburton_1f
Posts: 61
Joined: Fri Sep 28, 2018 12:24 am

Slow Step

Can someone explain to me why the slowest step in a reaction process determines the overall rate law for the reaction?

Lopez_Melissa-Dis4E
Posts: 66
Joined: Fri Sep 28, 2018 12:20 am

Re: Slow Step

You can only go as fast as your slowest reaction, therefore it is determines your overall rate law.

Eric Quach 1C
Posts: 30
Joined: Fri Sep 28, 2018 12:20 am

Re: Slow Step

Another way to put it would be that there is a bottleneck at the slow step. For example if there are 3 steps in a reaction and step 2 is the slow step, it doesn't matter if step 1 and 3 are almost instantaneous as step 2 must finish occurring before step 3 which completes the reaction.

Celine Cheng 1H
Posts: 33
Joined: Fri Sep 28, 2018 12:21 am
Been upvoted: 1 time

Re: Slow Step

What would happen if you have 2 slow steps? Is the slower step still the determining rate? Is having more than 2 slow steps possible?

Chris Freking 2G
Posts: 60
Joined: Fri Sep 28, 2018 12:29 am

Re: Slow Step

Celine Cheng 1H wrote:What would happen if you have 2 slow steps? Is the slower step still the determining rate? Is having more than 2 slow steps possible?

You can still have multiple "slow" reactants, but ultimately the slowest one will still determine the overall rate law.

(An extremely small bottleneck will still be a bottleneck for another small bottleneck)

Dong Hyun Lee 4E
Posts: 68
Joined: Fri Sep 28, 2018 12:23 am

Re: Slow Step

How do you determine the slowest step then? is it the lowest k value?