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Non Life Sciences => Chemistry => Topic started by: Chemistry4me on 27/05/2009 05:19:21

Title: Why do catalyst effectively lower the activation energy of chemical reactions?
Post by: Chemistry4me on 27/05/2009 05:19:21
Why do catalyst effectively lower the activation energy of chemical reactions?  [:-X]
Title: Why do catalyst effectively lower the activation energy of chemical reactions?
Post by: lightarrow on 27/05/2009 07:42:11
Quote from: Chemistry4me on 27/05/2009 05:19:21
Why do catalyst effectively lower the activation energy of chemical reactions?  [:-X]
It depends on the reaction and on the catalyst.
Title: Why do catalyst effectively lower the activation energy of chemical reactions?
Post by: Chemistry4me on 27/05/2009 07:52:00
Let's just say something like concentrated sulfuric acid when mixing an alcohol and a carboxylic acid to form an ester.
Title: Why do catalyst effectively lower the activation energy of chemical reactions?
Post by: Chemistry4me on 27/05/2009 07:56:07
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?
Title: Why do catalyst effectively lower the activation energy of chemical reactions?
Post by: Steph on 27/05/2009 12:55:47
Generally I believe the catalyst provides an alternative reaction pathway that has a lower activation energy, thus increasing the rate of reaction.
Title: Why do catalyst effectively lower the activation energy of chemical reactions?
Post by: lightarrow on 27/05/2009 17:00:22
Quote from: Chemistry4me on 27/05/2009 07:56:07
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.
Title: Why do catalyst effectively lower the activation energy of chemical reactions?
Post by: Bored chemist on 27/05/2009 19:17:48
Quote from: Chemistry4me on 27/05/2009 05:19:21
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)
Title: Why do catalyst effectively lower the activation energy of chemical reactions?
Post by: Chemistry4me on 27/05/2009 20:48:05
Okay, I don't mean to sound rude but those are all answering 'how' but not 'why' catalysts do this.
Title: Why do catalyst effectively lower the activation energy of chemical reactions?
Post by: Steph on 27/05/2009 20:58:18
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.
Title: Why do catalyst effectively lower the activation energy of chemical reactions?
Post by: Chemistry4me on 27/05/2009 21:11:46
Yes, the 'why' always needs a bit more explanation than the 'how'.
Title: Why do catalyst effectively lower the activation energy of chemical reactions?
Post by: lightarrow on 29/05/2009 10:52:03
Quote from: Chemistry4me on 27/05/2009 20:48:05
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...  [:)]
Title: Why do catalyst effectively lower the activation energy of chemical reactions?
Post by: Chemistry4me on 29/05/2009 11:03:39
Yeah...maybe. Reluctantly.