G

Gibbs Free Energy

ΔG = ΔH − TΔS | ΔG° = −RT ln K
Quick Reference
Formula / NotationΔG = ΔH − TΔS | ΔG° = −RT ln K
Also Known AsGibbs free energy, Gibbs energy, Free enthalpy

What is Gibbs Free Energy?

A thermodynamic state function (G) that predicts the spontaneity of a process at constant temperature and pressure: ΔG = ΔH - TΔS. A negative ΔG indicates a spontaneous process; positive ΔG indicates non-spontaneous. At equilibrium, ΔG = 0. Named after Josiah Willard Gibbs.

Formula & Notation

ΔG = ΔH − TΔS | ΔG° = −RT ln K

Other Names / Synonyms: Gibbs free energy, Gibbs energy, Free enthalpy

Properties & Characteristics

State function at constant temperature and pressure. ΔG < 0: spontaneous (exergonic). ΔG > 0: non-spontaneous (endergonic). ΔG = 0: system at equilibrium. Relates to equilibrium constant: ΔG° = −RT ln K. Relates to cell potential: ΔG° = −nFE°. At 298K, RT = 2.479 kJ/mol. Standard Gibbs energies of formation (ΔGf°) are tabulated for all common substances.

Uses & Applications

Predicting reaction spontaneity. Calculating electrochemical cell voltages. Biochemistry: ATP hydrolysis (ΔG° = −30.5 kJ/mol) drives metabolic reactions. Industrial process optimization. Calculating maximum work extractable from reactions. Protein folding stability analysis. Drug-receptor binding energy calculations.

Safety Information

Theoretical concept. Large negative ΔG values indicate highly exothermic or entropy-driven reactions that may proceed explosively — critical to recognize when designing experiments.

Always consult the SDS/MSDS before handling any chemical. This information is for educational purposes only.

Key Facts

Term Gibbs Free Energy
Formula ΔG = ΔH − TΔS | ΔG° = −RT ln K
Synonyms Gibbs free energy, Gibbs energy, Free enthalpy

Frequently Asked Questions

A thermodynamic state function (G) that predicts the spontaneity of a process at constant temperature and pressure: ΔG = ΔH - TΔS. A negative ΔG indicates a spontaneous process; positive ΔG indicates non-spontaneous. At equilibrium, ΔG = 0. Named after Josiah Willard Gibbs.

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