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Homework Help: Redox equations

  1. Aug 22, 2007 #1
    1. The problem statement, all variables and given/known data
    Write the half equation for the cathodic reaction of oxygen

    3. The attempt at a solution
    Now I know that the cathodic reaction will be reduction and so the oxygen will be gaining electrons. I thought I had the answer from the lecture notes, but then I thought of another possible equation that would work too and I don't know which one is right??

    The two equations are as follows:
    equation from notes( the notes say that this is the most common)
    [tex]O_2 + 2H_2O + 4e^- ->4OH^-[/tex]

    the equation I came up with
    [tex]O_2 + 4H^+ + 4e^- ->2H_2O[/tex]

    Are these just two possible half equations for the cathodic reaction of oxygen or is one wrong??

    Thanks for your time
  2. jcsd
  3. Aug 24, 2007 #2


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    Staff Emeritus
    Science Advisor
    Gold Member

    I think we need more context here. Both reactions are legal, and likely occur at quite different potentials, so additional details are necessary.
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