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  1. Apr 29, 2005 #1

    This is a followup to my previous post: thanks for the advice on the two questions. I got the HH one. That was quite easy.

    However, I'm not getting this one correctly:

    N2O4 --> 2NO2
    Delta G is 2.8kJ (under standard conditions). At what temp will it become spontaneous?

    So. I know Gibb's is: Delta G = Delta H - T(delta S)

    The delta H for N2O4 is 9.66 and NO2 is 33.85
    The delta S for N2O4 is 304.3 and NO2 is 240.46
    This is per my book

    I plug those into the Delta H and Delta S equations:
    2(33.85) - 9.66 = 58
    2(240.46) - 304.3 = 176.9

    T = Delta H / Delta S
    This comes out to 0.328 K

    That can't be right! What did I do wrong?
  2. jcsd
  3. Apr 29, 2005 #2


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    Homework Helper

    You should be able to find a derivation which includes the [tex] \Delta G^{0},~and~ \Delta G [/tex] The reaction is spontaneous when [tex] \Delta G [/tex] is zero. Try to find the simplest equation.
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