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Catalyst function

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joonkimdds

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I learned from my biology class that all catalyst does is lowering the activation energy to speed up the reaction without being consumed.

so how can it change the reaction mechanism if it's not being consumed or add anything?

and how does it change the specific rate constant too?
 

PreDent2009

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The catalyst or enzyme is able to lower the Ea of the reaction because it alters the shape of the active site so when the substrate binds it is actually sitting in a conformation that more closely resembles the transition state complex. By doing so it helps to provide an alternate mechanism with a lower Ea so the reaction can proceed faster. With all this being said, the catalyst does not change the equilibrium of the reaction when talking about chemistry, it just helps to reach the equilibrium faster. It does change the rate constant of the specific reaction though, but not the rate constant of the overall rxn. I hope this helps.
 

joonkimdds

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let's say there is a reaction with 10 step mechanism (Organic chemistry for example).

if we use catalyst, does it actually make that 10 steps into 5 steps or something like that?
 

Sea of ASH

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no, if that 10 steps normally takes 5 mins, for example, the reaction with a catalyst takes, lets say, 1 min. the same reaction occurs, just the rate is increased.

what a catalyst actually does is bring the reactants together so that it is easier to form the transitional state. the activation energy is the engery required to form the TS. the formation of the TS is the "rate determining step" also. so catalyst brings the reactants together to form the TS alot quicker without being used itself at all.
 

joonkimdds

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no, if that 10 steps normally takes 5 mins, for example, the reaction with a catalyst takes, lets say, 1 min. the same reaction occurs, just the rate is increased.

what a catalyst actually does is bring the reactants together so that it is easier to form the transitional state. the activation energy is the engery required to form the TS. the formation of the TS is the "rate determining step" also. so catalyst brings the reactants together to form the TS alot quicker without being used itself at all.

I see. I understand how it lowers activation energy and change the rate determining step, but I still don't understand how it "changes" the mechanism if 10 step still remains 10 step.
 
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