1. The problem statement, all variables and given/known data Calculate the pressure at which graphite spontaneously changes to diamond. T = 298.15 K (isothermal) Vdiamond - Vgraphite = -2 x 10-6m3/mol At 273.15K and 1 bar (105 Pa): ΔGf graphite = 0 ΔGf diamond = 2.9 kJ/mol i.e. graphite is the more stable and preferred form of carbon in the above conditions. 2. Relevant equations Not really sure here... Could be anything. Perhaps useful is: G = H - TS But I don't see where P fits in. 3. The attempt at a solution Well, I know G will be 0 at the pressure I am trying to identify (i.e. graphite and diamond will be in equilibrium, with equal tendency for the carbon to form either).