Using G (measure of free energy) to determine wether the reaction 4Fe(s)+3O2(g)-> 2Fe2O3(s) is spontaneous at 25C, given that H=.393kcal and S=-0.13 kcal/(mol*K).

Question

Is the reaction more or less spontaneous at 1000C assuming that H and S remain constant with temperature?

G at 25C is -354.26(and im not sure what type of units to put it in)
G at 1000C is -227.51.

I do not know how to tell if the reaction is spontaneous at 25C or how to tell if it is more or less spontaneous at 1000C.

Thanks for your help!!!

Answer 1

The sign of DG determines if a reaction is spontaneous or not.

* DG < 0: the reaction is spontaneous
* DG > 0: the reaction is not spontaneous
* DG = 0: the reaction is at equilibrium .

Be certain you worked temperatures in K, not C.

Answer 2

I worked in K.... so at either temp the reaction is not spontaneous? but it is more spontaneous at 1000C?

Answer 3

IT is negative, so spontaneous at both temps. It is more negative at 25C.