Friday, May 17, 2019

thermodynamics - Catalytic energy profiles (is this Wikipedia image misleading?)



I am looking at the image below from the Wikipedia page for energy profiles in chemistry. I do not understand why the "$E_a$ (with catalyst)" is labeled as it is. I would argue that is not the activation barrier with the catalyst. Shouldn't all of the individual steps need to be considered to get the rate of production of product (or, if one step has an especially high barrier, then that step can be assumed to be rate-limiting and that step's $E_a$ is the barrier with the catalyst)? I suppose in other words, if I do $r = A\exp(-E_a/k_{B}T)$ where $E_{a}$ is the activation energy with catalyst, that will not get me the rate, right?


Activation energy with and without catalysts


For the record, I have taken grad-level courses in chemistry, but I got myself into a position of questioning everything I once learned and here I am.




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