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Is the oxidization of a substance ever exothermic?

  1. Oct 29, 2009 #1
    Like the question states, if you remove the electrons from an atom using some catalyst, will that reaction be exothermic or neutral. For example oxidization of hydrogen using platinum.

    H2 + Pt = PtH+2 + 2e-

    Would this reaction absorb or emit any heat? I wouldn't think so since I think this reaction can occur almost spontaneously as the Pt reduces the H2 bond strength to 0eV or am I just talking nonsense here?
     
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  3. Oct 29, 2009 #2

    chemisttree

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    You are confusing spontaneity with enthalpy. Oxygen and hydrogen spontaneously combine to form water and that reaction is plenty exothermic.
     
  4. Oct 29, 2009 #3
    Yes, I realize the reaction between hydrogen and oxygen is exothermic, but what about the reaction of hydrogen with platinum?
     
  5. Oct 30, 2009 #4

    chemisttree

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    What reaction is that? The one you show doesn't make any sense. Do you have a reference for it?

    I know that platinum oxide is reduced in the presence of hydrogen (producing water) to platinum metal but I have never seen platinum itself reacting with hydrogen to generate acid and 2 electrons (where do they go?). The "reaction" you suggest is simply the adsorption of hydrogen on the surface of platinum. It is likely an exothermic process since it is known to occur and entropy is decreasing. I don't think that any electrons or acid are produced...
     
  6. Nov 3, 2009 #5
    here's a few exothermic oxidations:

     
    Last edited by a moderator: Sep 25, 2014
  7. Nov 4, 2009 #6
    Hi,

    This video is very good to keep all the facts in mind, as this is giving me a pure example of exothermic oxidations which are no doubt very serving.


    Thanks!
     
    Last edited by a moderator: Sep 25, 2014
  8. Nov 7, 2009 #7
    Sorry for my nonsense, I should have been more clear. I'm referring to the reaction or maybe you would call it a process, where hydrogen is chem-absorbed by platinum and the hydrogen molecules split from a single diatomic molecule into two monotonic molecules and both are oxidized (no O2 present). If this happens at a three phase region where one of those phases is an electrolyte and the other phase is an electronically conductive material, the electrons have the ability to separate from the hydrogen creating cations. The cations of course can then migrate through the electrolyte. If you need references I can post a few, but I thought this was a rather common process in electrochemistry?

    Again, sorry if I'm not making any sense, I'm an ME trying to learn electrochemistry.
     
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