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Chemistry Forums for Students => Physical Chemistry Forum => Topic started by: francisco on November 05, 2016, 04:14:27 AM

Title: Gibbs free energy
Post by: francisco on November 05, 2016, 04:14:27 AM

1) The free standard energy of formation for a pure element in its most stable form is defined to be zero.
2) The enthalpy of formation of the same compound is also defined to be zero.
3) The entropy of the same compound must not be zero if not at @ 0 Kelvin and a perfect crystalline substance.
4) But G=H-TS
Hence G= 0 + TS where T and S may both be greater than zero. Hence G < 0 and different from zero for a pure elemental substance, which contradicts 1)

Please help.

Title: Re: Gibbs free energy
Post by: mjc123 on November 05, 2016, 07:32:54 PM

G is not the standard free energy of formation. What is the definition of the latter?