Given the reaction of diamond converting to graphite

Question

2C (s diamond)==>2C (s graphite)

 

Determine ΔG at 298L and determine if this reaction is spontaneous or not. What does the ΔG say about the rate of this reaction?

 

ΔH°f (C (s) diamond)=1.9kJ/mol

S°(C (s) diamond=2.38J/mol

S°(C (s)graphite)=5.74J/mol

Answer 1

∆G says nothing about the rate of the reaction.  It only provides information about spontaneity.

∆G = ∆H - T∆S

Plug in values (be careful of units; note ∆H is in kJ/mol and others are J/mol).

Do this for the forward and reverse reactions AS WRITTEN.

If ∆G is negative, the reaction is spontaneous.

 

You probably realize that diamonds are made from solid carbon, but it takes a very long time under a great deal of pressure. Thus, the reaction of C(s) ==> diamond(s) would be spontaneous but the rate of reaction is extremely so.  The numerical answer you get from the above equation should agree with this.