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Homework Help: Chem. Half-Reactions

  1. Oct 25, 2007 #1
    Determine concentration of H2O2 with Titration of KMnO4

    Balance the equation and create a net ionic equation then balance using redox techniques and replace spectator ions

    Balanced Equation:
    5H2O2 + 2KMnO4 + H2SO4 ==> K2SO4 + MnSO4 + H2O + O2

    My Work:
    I eliminated all spectators and my net ionic equation was

    16H(+) + 18O(2-) ==> 8H20 + 5O2

    This cannot be correct, since putting this into a half-reaction

    8H2O + 16H(+) ==> 8H2O + 16H(+) there is no need for e- and therefore is not a redox reaction. If I have the correct ionic equation I'm sure I can figure out the rest
  2. jcsd
  3. Oct 26, 2007 #2


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    Half reactions are reactions where the oxidant's reaction is shown separately from the reductant's reaction. It can be generalized as:

    [O] + e- ----> [O]- ( or [O]+ + e- ------> [O] )


    [R] -------> [R]+ + e- ( or [R]- ------> [R] + e- )

    where [O] is the oxidant and [R] is the reductant.

    In your example what is the reductant and the oxidant? Hint: H+ is neither...
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