Rate Law

[sos5]

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Can intermediates or catalysts occur in the rate law if they are in the slow step therefore rate step?

 

[butters221]

Yes. They are reactants that change the rate of the rate determining step. The reaction wouldn't even occur if you didn't have any of the intermediate (a reactant for this step) and the reaction would take much longer if you didn't have the catalyst.

 

[sos5]

I don't think intermediates can be part of rate law. Although, in the Princeton Review Mcat General Chemistry book the answer includes the intermediate in the rate law. My understanding is intermediates are transient and form when reactants are forming products they are not reactants therefore can't be in rate law.

 

[dudewheresmymd]

Catalysts can appear. Intermediates generally do not. Look at what they give you, if you can rearrange the equation from a fast step prior to the slow step, do so, if not, then go with the best answer.

References:

"Other examples of species not in the balanced reaction occuring in the rate law would include catalysis, where a catalyst does not normally appear in the balanced reaction but does appear in the rate law."

http://www.chem.arizona.edu/~salzmanr/480a/480ants/lindeman/lindeman.html

http://chemwiki.ucdavis.edu/Physical_Chemistry/Kinetics/Rate_Laws/Reactions/Reaction_Mechanisms