Intermediates in Rate law


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Chew 2H
Posts: 34
Joined: Fri Sep 29, 2017 7:05 am

Intermediates in Rate law

Postby Chew 2H » Sun Mar 11, 2018 11:20 pm

Clarification:
When we write rate law based on order, we only include the intermediates if we're writing the rate law for the specific reaction (say step 1 or step 2) right? If it's the overall reactions, we always have to cancel out the intermediates?

Christina Cen 2J
Posts: 53
Joined: Sat Jul 22, 2017 3:01 am

Re: Intermediates in Rate law

Postby Christina Cen 2J » Sun Mar 11, 2018 11:38 pm

Yes, the reaction for the final rate law should not contain intermediates. Solve for the intermediates in terms of the reactants that should be in the final reaction and substitute it instead of the concentration of the intermediate if you have to.

Vincent Chiang 1L
Posts: 54
Joined: Fri Sep 29, 2017 7:05 am

Re: Intermediates in Rate law

Postby Vincent Chiang 1L » Sun Mar 11, 2018 11:39 pm

Yes, when writing the overall rate law, you shouldn't include intermediates, only substances that are in the overall reaction.

Ashley Garcia 2L
Posts: 33
Joined: Fri Sep 29, 2017 7:05 am

Re: Intermediates in Rate law

Postby Ashley Garcia 2L » Mon Mar 12, 2018 10:50 am

For the overall rate law you should not include intermediates (because they are produced and then used up by the reaction). The rate law should only include reactants.

Example:
Step 1: A + B → C
Step 2: C → D
Overall: A + B → D (C is the intermediate)
rate law = k[A][B] (do not include [C] in the rate law)


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