Free energy calculating electromotive force from

A more complete description of this research will soon appear in the Journal of the American Chemical Society. The preparation of the cells so as to secure constancy and reprodudbility of the electromotive force values, the methods of making the measurements, the full experimental data, and thermodynamic calculations from them of other free-energy values will be there presented in detail. 

A chemical reaction can give out (or take in) energy in three forms heat, pressure-volume work, and electrical work. We now specify that the free-energy change excludes the work (P AV) done by or against a constant external pressure. This means that at constant pressure, the free-energy change is equal to minus the reversible electrical work, which is calculated from the reversible electromotive force. 

The most useful concept that biochemists have obtained from thermodynamics is that of free energy. By considering the free energy change one can tell whether a reaction may proceed spontaneously or whether it must be driven by other reactions. Further, one can calculate the amoimt of energy given off by a reaction or required by it, and this is a most important feature of many reactions. From free energy data one can easily calculate equilibrium constants and electromotive forces. 

Electromotive force series based on experimentally determined potentials or on potentials calculated from appropriate free energies have been developed for several molten solvents. Plambeck in 1966 critically reviewed and tabulated values for the LiCl-KCl eutectic (450°C), equimolar NaCl-KCl (700-900°C), NaF-KF eutectic (850°C), MgCla-NaCl-KCl eutectic (475 C), AlCla-NaCl-KCl (66-20-14 mole %) (218 C), Li2S04-K2SO4 eutectic (625°C), and Li2S04-Na2S04-K2S04 eutectic (575°C). By far the most extensive series is that for the LiCl-KCl eutectic, developed... 

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