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The standard Gibbs free energy of formation of a compound is the change of Gibbs free energy that accompanies the formation of 1 mole of that substance from its component elements, in their standard states (the most stable form of the element at 25 °C and 100 kPa). Its symbol is Δ f G˚.
The standard Gibbs free energy of formation (G f °) of a compound is the change of Gibbs free energy that accompanies the formation of 1 mole of a substance in its standard state from its constituent elements in their standard states (the most stable form of the element at 1 bar of pressure and the specified temperature, usually 298.15 K or 25 °C).
Hence, the main functional application of Gibbs energy from a thermodynamic database is its change in value during the formation of a compound from the standard-state elements, or for any standard chemical reaction (ΔG° form or ΔG° rx). The SI units of Gibbs energy are the same as for enthalpy (J/mol).
It describes how the Gibbs free energy, which was presented originally by Josiah Willard Gibbs, varies with temperature. [1] It was derived by Helmholtz first, and Gibbs derived it only 6 years later. [2] The attribution to Gibbs goes back to Wilhelm Ostwald, who first translated Gibbs' monograph into German and promoted it in Europe. [3] [4]
The basic question to be addressed is, then, how can the Helmholtz free energy change (ΔF = F B − F A) on moving between the two super states be calculated from sampling in both ensembles? The kinetic energy part in the free energy is equal between states so can be ignored. Also the Gibbs free energy corresponds to the NpT ensemble.
The Helmholtz free energy is in ISO/IEC standard called Helmholtz energy [1] or Helmholtz function. It is often denoted by the symbol F, but the use of A is preferred by IUPAC, [5] ISO and IEC. [6] These five common potentials are all potential energies, but there are also entropy potentials.
If the majority of group-contribution methods give results in gas phase, recently, a new such method [4] was created for estimating the standard Gibbs free energy of formation (Δ f G′°) and reaction (Δ r G′°) in biochemical systems: aqueous solution, temperature of 25 °C and pH = 7 (biochemical conditions). This new aqueous-system ...
Analogous to Hess's law which deal with the summation of enthalpy (ΔH) values, Bordwell thermodynamic cycles deal with the summation of Gibbs free energy (ΔG) values. Free energies used in these systems are most often determined from equilibriums and redox potentials, both of which correlate with free energy. This is with the caveat that ...