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Finding ΔG and K for a given redox reaction

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  1. Apr 5, 2009 #1
    1. The problem statement, all variables and given/known data

    Redox reaction:
    B-hydroxybutarate + 1/2O2 -> acetoacetate + H2O

    Half reaction 1:
    O2 + 4H+ + 4e- -> 2H2O (E = +0.816 V)

    Half reaction 2:
    acetoacetate + 2H+ + 2e- -> B-hydroxybutarate (E = -0.346 V)

    Using standard reduction potentials given,

    • calculate ΔG
    • calculate the equilibrium constant, K

    Conditions are the biochemist's standard state, pH 7, 298.15 K.

    2. Relevant equations

    ΔG = -nFΔE

    ln K = nFE/RT

    3. The attempt at a solution

    ΔErxn = (0.816 V) + (0.346 V)
    ΔErxn = 1.162 V

    ΔG = -nFΔE
    ΔG = -n(96485 C/mol)(1.162 V)

    n = ? (moles of electrons transferred)

    By writing out both half reactions, the electrons cancel out. Should there not be electrons left over on one side of the equation in order to determine the value of n?
     
    Last edited: Apr 5, 2009
  2. jcsd
  3. Apr 5, 2009 #2

    Borek

    User Avatar

    Staff: Mentor

    No, if electrons are left, reaction is not balanced.
     
  4. Apr 7, 2009 #3
    So 2 mol of e- per mol of product (n = 2)?
     
  5. Apr 12, 2009 #4
    Can someone please confirm this?
     
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