Why does the Gibbs free energy need to be minimized for an equilibrium? dG=dE+pdV−TdS But dE=Tds−pdV so it should be dG=0. Why dG is not always zero?

Daniella Reyes

Daniella Reyes

Answered question

2022-09-26

Why does the Gibbs free energy need to be minimized for an equilibrium?
d G = d E + p d V T d S
But d E = T d s p d V so it should be d G = 0. Why d G is not always zero?

Answer & Explanation

baselulaox

baselulaox

Beginner2022-09-27Added 8 answers

This formula isn't universally valid.
Free enthalpy's definition is G = E + P V T S, so, for a system without chemical reaction or phase transition:
d G = d E + P d V + V d P T d S S d T = V d P S d T
So if P and T are constant, then yes, dG will be zero.

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