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Gibbs function

Gibbs function (Gibbs free energy; symbol G or F) Generally defined in terms of changes in free energy: ΔF = ΔHTΔS, where H = enthalpy, T = absolute temperature, S = entropy. In a mixture of reactants, if ΔF is less than 0 a reaction may take place spontaneously, whereas if ΔF is positive energy must be supplied to the system for a reaction to occur at all. In geochemistry, the sign and magnitude of ΔF are important. The sign indicates whether a given reaction can occur spontaneously, and the magnitude indicates how far the reaction can go before equilibrium is attained.

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