Rate Determining Step

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305113590
Posts: 66
Joined: Fri Sep 28, 2018 12:28 am

Rate Determining Step

Postby 305113590 » Sun Mar 03, 2019 5:26 pm

How do we write a rate equation when there is a rate determining step along with several fast elementary steps?

Lexie Baughman 2C
Posts: 30
Joined: Sat Oct 06, 2018 12:16 am

Re: Rate Determining Step

Postby Lexie Baughman 2C » Sun Mar 03, 2019 5:35 pm

The rate-determining step is the slowest step in a reaction mechanism. Because it is the slowest, it determines the rate of the overall reaction. In a reaction with a slow initial step, the rate law will simply be determined by the stoichiometry of the reactants.

Michelle Nwufo 2G
Posts: 61
Joined: Fri May 18, 2018 3:00 am

Re: Rate Determining Step

Postby Michelle Nwufo 2G » Sun Mar 03, 2019 8:34 pm

Lexie Baughman 2C wrote:The rate-determining step is the slowest step in a reaction mechanism. Because it is the slowest, it determines the rate of the overall reaction. In a reaction with a slow initial step, the rate law will simply be determined by the stoichiometry of the reactants.



How do you determine whether a step in a reaction mechanism is slow or not?

Anna O 2C
Posts: 98
Joined: Fri Sep 28, 2018 12:19 am

Re: Rate Determining Step

Postby Anna O 2C » Sun Mar 03, 2019 10:19 pm

A way that I think about the slow vs fast rates is with cooking. The entire length of the cooking session will be determined by the step that takes the longest and has the biggest overall effect on the time duration (example would be the baking in the oven compared to measuring the ingredients which takes seconds).

Lexie Baughman 2C
Posts: 30
Joined: Sat Oct 06, 2018 12:16 am

Re: Rate Determining Step

Postby Lexie Baughman 2C » Wed Mar 13, 2019 2:59 pm

As far as practice problems I've seen/done, they'll have to tell you the slow step in a mechanism, and depending whether the slow step involves an intermediate or not, you'll have to tailor your approach.

105169446
Posts: 32
Joined: Fri Sep 28, 2018 12:16 am

Re: Rate Determining Step

Postby 105169446 » Sat Mar 16, 2019 11:57 pm

What happens if the slow step has an intermediate in it?

CristinaMorales1F
Posts: 31
Joined: Fri Feb 16, 2018 3:01 am

Re: Rate Determining Step

Postby CristinaMorales1F » Sun Mar 17, 2019 12:25 am

can a slow step have an intermediate?

CristinaMorales1F
Posts: 31
Joined: Fri Feb 16, 2018 3:01 am

Re: Rate Determining Step

Postby CristinaMorales1F » Sun Mar 17, 2019 12:26 am

How does a bottleneck work and how does this determine rate?

davidryan3f
Posts: 63
Joined: Fri Sep 28, 2018 12:23 am

Re: Rate Determining Step

Postby davidryan3f » Sun Mar 17, 2019 12:44 am

The slow step can't have intermediates. You substitute them using values in the other steps.

KHuang1L
Posts: 60
Joined: Fri Sep 28, 2018 12:19 am

Re: Rate Determining Step

Postby KHuang1L » Sun Mar 17, 2019 4:27 pm

The rate law is determined by the rate determining step. If there are intermediates involved, then modify the rate law so that they are not included.


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