[AlexRM]

Hey guys,
This problem has me stumped.  I am given the following table of information:

Property	CaCO3 (calcite)	CaCO3 (argonite)
ΔHo kj/mol(formation)	-1206.87	-1207.04
ΔGo kj/mol(formation)	-1128.76	-1127.71
density, g/cm3	2.71	2.93

And I have to find the pressure required to make the conversion calcite(s)  argonite(s) spontaneous at 25 degrees celcius.  I am also given that the molecular weight of CaCO3 is 80 g/mol. 

I found the standard ΔG and ΔH of reaction to be +1.07 kJ/mol and 0.17 kJ/mol, respectively.
However, beyond that, I have no idea how to find the pressure required.
I tried using the relation ΔG = ΔH - TΔS, so that ΔH - TΔS < 0 for a spontaneous process.  I then substituted a bunch of things but just ended up with everything cancelling out

Any ideas how to do this problem?

[Schrödinger]

First step : calculate entropy using given data, at standard conditions. Then use that to set up equilibrium conditions, assuming entropy doesn't change much with temperature