Free Energy and Equilibrium Constant
The relation connecting the standard Gibbs energy change of a reaction to its equilibrium constant.
Formula / equation
ΔG° = −RT ln K
Unit
kJ/mol
In depth
The equation converts a thermodynamic quantity into a measurable equilibrium position and back again. Because the relationship is logarithmic, a modest free energy change produces an enormous change in K: about 6 kJ/mol shifts K by a factor of ten at room temperature.
Examples in the real world
ΔG° = −40 kJ/mol corresponds to K ≈ 10⁷ at 298 K, meaning the reaction goes essentially to completion.