Definition of electro-chemical potential of the substance:

u(x,T,v) = u°(T) + R*T*ln(gamma*x) + z*F*v

u°(T) = DfG(T) = DfH - T * DfS


x .. mole fraction of the substance in the solution

T .. temperature in Kelvins

v .. eletric potential of the solution

z .. elementary charge of the substance (like -1 for electron, +2 for Ca^2+)

R .. gas constant

F .. Faraday constant

gamma .. activity coefficient

u°(T) .. chemical potential of pure substance

DfG(T) .. free Gibbs energy of formation of the substance at current temperature T.

DfH .. free enthalpy of formation of the substance

DfS .. free entropy of formation of the substance

Be carefull, DfS is not the same as absolute entropy of the substance S° from III. thermodinamic law! It must be calculated from tabulated value of DfG(298.15 K) and DfH as DfS=(DfH - DfG)/298.15.



Marek Matejak, Charles University, Prague, Czech Republic

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