Hi,

I am a bit confused about calculation of Gibbs free energy for the folowing equation:

CH4 = C + 2H2

I considered C as graphite, CH4 and H2 as gas.

According to my calculation, DH = 74, DS = 0.080844

So the reaction will be spontaneous at 915 k (642 C) according to DG = DH - T*DS (putting DG =0)

But I have found two papers where they indirectly mentioned that they found DH =90 for this equation which gives spontaneous reaction temperature at 1113 k (840 C).

Can anyone please explain??

Also, why do we consider C as graphite, not as gaseous? Is it because of temperature??

regards,

TH