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Free energy question involving Kp and deltaG

  1. Dec 1, 2012 #1
    1. The problem statement, all variables and given/known data

    The following reaction takes place at standard conditions

    4NH3(g)+6NO(g)----->5N2(g)+6H20

    A)calculate reaction enthalpy and Gibbs reaction energy

    B)Calculate Kp


    2. Relevant equations

    the table gives the following values for deltaG0f[X]
    NH3(g)=-16.5 Kj/mol
    NO(g)=87.6 KJ/mol
    H20(g)=-228.6 KJ/mol

    ln(Kp)=-deltaG/(RT)


    3. The attempt at a solution

    I finished part a) and found gibbs reaction energy to be -1815 KJ

    For part b) i am unsure of what to enter for deltaG in the equation ln(Kp)=-deltaG/(RT). Do I use the reaction energy calculated from part a), deltaG for NH3, NO, or H20? Any help is appreciated, thanks!
     
  2. jcsd
  3. Apr 20, 2015 #2
    you would use the standard DG found by this formula:
    ∑nΔGoproducts - ΣmΔGoreactants
     
  4. Apr 20, 2015 #3
    -the n and m being the coefficients for each molecule
     
  5. Apr 20, 2015 #4
    You use the ΔG0 that you calculated in part a (I didn't check your arithmetic). (Also, that should not be a ΔG in the equation; it should be ΔG0). To get the standard reaction enthalpy, you need to know the standard heats of formation. Did they give you these?

    Chet
     
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