Gibbs Free Energy

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Equation / Last modified by Administrator on 2016/05/20 16:46
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MichaelBartmess.Gibbs Free Energy

The equation defines the Gibbs Free Energy of reaction, which is analogous to potential energy defining the process-initiating work available to trigger a reaction.  As such it is defined in units of energy / amount of substance (J/mol).

`Delta _G=-R * T * ln (K_a)`

  • R = ideal gas constant
  • T = temperature (Kelvin)
  • `K_a` = natural log of the reaction quotient


A most important thermodynamic property is one termed the "free energy of a reaction" also called the change in Gibbs Free Energy (`Delta_G`). Gibbs energy is defined as the chemical potential that is minimized when a system reaches equilibrium at constant pressure and temperature.  The Gibbs Free Energy in this definition is the state in which a process can occur while maintaining constant pressure and temperature. Understanding the free energy of a reaction allows one to determine under what conditions a chemical or biological reaction will proceed, the state of equilibrium and how to compute the equilibrium constant (`K_eq`) of the reaction.