Calculate the temp at which the reaction (2POCL3(g) - 2PCl3(g)+O2(g))would become spontaneous. Given: DH= +572kJ and DS= 179 J/K.

Question

Calculate the temp at which the reaction (2POCL3(g) -> 2PCl3(g)+O2(g))would become spontaneous. Given: DH= +572kJ and DS= 179 J/K.

Would the answer be 298 K? I found DG to be 518.658 kJ, and then plugged in all the values to DG= DH-TDS.
Or, should I ignore the DG, set DH-TDS to = 0, and find the answer to be about 3195.53 K?
Which is the proper way to go about answering this question?

DrBob222 · Answer

I think you do the latter. Set DG = 0 (or -1 since, technically, DG = 0 at equilibrium). I think these are handled by setting DG = 0, then stick an appendix to the answer that says "anything above this T."