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Homework Help: Gibb's free energy (very simple one)

  1. Mar 29, 2007 #1
    1. The problem statement, all variables and given/known data

    Calculate the equilibrium constant for the reaction forming nitric oxide at room temperature, 25C. G= 1.73x10^5 J/mol, H = 180.5KJ/mol an S = 24.8J/(mol.K)

    2. Relevant equations

    ln K = -G/RT

    3. The attempt at a solution

    I subsiuted ln K = (-1.73x10^5) / (8.3145x298.15)
    ln K = -69.78
    I'm getting K as 4.95*10^-31

    but the computer (where I submit online assignment ) is saying its wrong ... I've only one single attempt left ..can anyone see where I'm wrong.
    Thanks and immediate help please!
    Last edited: Mar 30, 2007
  2. jcsd
  3. Mar 30, 2007 #2


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    Science Advisor
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    Gold Member

    Please show some more work. In particular, how did you obtain the value for G? What units did you use for R and S? Example: H is in KJ/mol and S is in J/molK. When I mess up these calculations, it is usually related to units.

    BTW, for a very useful compilation of R in various units, consult the CRC Handbook of Chemistry and Physics. In the 84th edition (2003-2004), a very complete table is printed on page 1-54.
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