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I tried to find the value of equilibrium constant several times. I failed..

the value of equilibrium constant at 500K has enthalpy 250kJ/mol and entropy 48J/mol*K

the answer is $ 2.45*10^{-24} $

which formula do I have to use?

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    $\begingroup$ What formulas have you tried? $\endgroup$
    – Lighthart
    Commented Mar 22, 2016 at 19:44
  • $\begingroup$ @Lighthart I have used $lnK=-delta/RT + deltaS/R$ $\endgroup$
    – devDNA
    Commented Mar 22, 2016 at 19:46

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$\Delta G=\Delta H - T \Delta S = 250-48 \times 10^{-3} \times 500 = 226 KJ/mol$
$K=exp(-\frac{\Delta G}{RT})=exp(-\frac{226 \times 10^3}{8.314 \times 500})=2.45 \times 10^{-24}$

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    $\begingroup$ Oh... my problem was that I did not multiply 10^-3 to entropy. Thank you. $\endgroup$
    – devDNA
    Commented Mar 22, 2016 at 19:58

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