Table of chemical potentials
(compiled by Dr. Georg Job)
In the tables the values of approximately 1300 substances can be found, taken from the sources mentioned in the bibliography.
The scale is defined by:
- µ = 0 for the elements in their most stable modification (except of phosphorus) under standard conditions, nuclear entropy neglected;
- µ = 0 for H+aq under standard conditions, entropy of H+aq equates zero;
- µ = 0 for egas under standard conditions. Therefore, the values for gaseous and hydratized ions are not directly comparable. Because of the neglection of the nuclear entropy this is also true for substances with a nuclear composition which differs from the natural one (isotopes, ortho- and parahydrogen).
Without further informations the values are valid
- under standard conditions (T = 298 K, p = 101,3 kPa),
- for dissolved substances at the standard concentration (1000 mol/m3),
- for gaseous or dissolved substances in an idealized state without intermolecular interactions,
- for all substances in the natural isotope composition of the elements.
The µ values are expressed by the SI coherent unit “Gibbs”, abbreviated to G (= J/mol) (Since we constantly deal with values of the chemical potential, we are justified in giving this unit its own name, “Gibbs,” in a manner analogous to “Volt” for the electric potential difference.) The name has been proposed by E. WIBERG („Die chemische Affinität“, 1972, p. 164) to honour Josiah Willard GIBBS (1839 – 1903) who first introduced the concept of chemical potential.
Instruction for use: The sequence of the elements in the molecular formulas is as follows:
electropositive elements (metals, noble gases) - electronegative elements (non-metals without noble gases, O, H) - oxygen - hydrogen.
The formula of water for example is expressed as OH2, that of sulfuric acid as SO4H2.