Gibbs Free Energy - Useful Identities

Useful Identities

(for constant temperature)
(see Chemical equilibrium)

and rearranging gives

which relates the electrical potential of a reaction to the equilibrium coefficient for that reaction (Nernst equation).

where

ΔG = change in Gibbs free energy, ΔH = change in enthalpy, T = absolute temperature, ΔS = change in entropy, R = gas constant, ln = natural logarithm, ΔrG = change of reaction in Gibbs free energy, Δr = standard change of reaction in Gibbs free energy, K = equilibrium constant, Qr = reaction quotient, n = number of electrons per mole product, F = Faraday constant (coulombs per mole), and E = electrode potential of the reaction. Moreover, we also have:

which relates the equilibrium constant with Gibbs free energy.

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