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Author Topic: Why do catalyst effectively lower the activation energy of chemical reactions?  (Read 5010 times)

Offline Chemistry4me

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Why do catalyst effectively lower the activation energy of chemical reactions?  :-X


 

Offline lightarrow

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Why do catalyst effectively lower the activation energy of chemical reactions?  :-X
It depends on the reaction and on the catalyst.
 

Offline Chemistry4me

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Let's just say something like concentrated sulfuric acid when mixing an alcohol and a carboxylic acid to form an ester.
 

Offline Chemistry4me

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Or is that one a bit fuzzy because it is also a dehydrating agent?
How about using manganese dioxide to speed up the decomposition of hydrogen peroxide?
 

Offline Steph

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Generally I believe the catalyst provides an alternative reaction pathway that has a lower activation energy, thus increasing the rate of reaction.
 

Offline lightarrow

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Or is that one a bit fuzzy because it is also a dehydrating agent?
How about using manganese dioxide to speed up the decomposition of hydrogen peroxide?
If I rember well, in this case (as Steph wrote and as it is in a lot of other cases) MnO2 reacts with H2O2 in a way that has a lower activation energy than the direct decomposition of the peroxide, forming intermediates of reaction which then, with another low-energy of activation, give again MnO2 and also O2 and water.
« Last Edit: 27/05/2009 17:02:22 by lightarrow »
 

Offline Bored chemist

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Why do catalyst effectively lower the activation energy of chemical reactions?  :-X
Because otherwise we wouldn't call them catalysts.

(OK,I know about negative catalysts too)
 

Offline Chemistry4me

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Okay, I don't mean to sound rude but those are all answering 'how' but not 'why' catalysts do this.
 

Offline Steph

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Ahhh WHY they work may not be as easy a question to answer, I certainly can't answer it. Though chemical reactions basically work on the premise of the atoms involved filling their outer energy level with electrons, therefore achieving stability. Perhaps the answer is something along these lines.
 

Offline Chemistry4me

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Yes, the 'why' always needs a bit more explanation than the 'how'.
 

Offline lightarrow

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Okay, I don't mean to sound rude but those are all answering 'how' but not 'why' catalysts do this.
You mean as the difference between "how" someone killed a person and "why" he did it?  :)
What is the meaning of "why" in the case of atoms? If you know "how" you authomatically know "why". Atoms don't have psychological motivations...  :)
 

Offline Chemistry4me

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Yeah...maybe. Reluctantly.
 

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