Find the temperature at which Kp=4.00 for the reaction N2O4(g) <==> 2NO2(g).

Given at 25 degrees C aka 298K,
For NO2(g), Delta H = 33.85 kJ/mol, Delta S = 240.46 J/mol*K
For N2O2(g) Delta H = 9.66 kJ/mol, Delta S = 304.3 J/mol*K

Assume that Delta H and Delta S are independent of temperature.

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The answer is 79 degrees Celsius.. but I can't seem to get it. My Delta G is 5.41 and it just doesn't work out..

Could somebody help me?

dG = -rTln(K)
dG = dH - TdS, i believe you will want to convert delta H to joules first.

so then:

dH - TdS = -RTln(K)
are you making sure you are using right gas constant? sorry, dont have a calculator so i cant really test out the math.

Yea, I've done all that.. gas constant with joules in it.. 8.314 J

I've used the dG from the appendix too.. I dont know how to properly add the dH and dS.. for some reason I cant get the right temp.. and if I used the right temp, I cant get the delta G

Free energy = system - surrounding

you have to convert kp to kc to use in the equation G=-rtlnKc