Gibbs energies ionic strength

The relationships of the type (3.1.54) and (3.1.57) imply that the standard electrode potentials can be derived directly from the thermodynamic data (and vice versa). The values of the standard chemical potentials are identified with the values of the standard Gibbs energies of formation, tabulated, for example, by the US National Bureau of Standards. On the other hand, the experimental approach to the determination of standard electrode potentials is based on the cells of the type (3.1.41) whose EMFs are extrapolated to zero ionic strength. 

One of the main models which is available in CALPHAD calculation programmes is that based on Pitzer (1973, 1975), Pitzer and Mayorga (1973) and Pitzer and Kim (1974). The model is based on the development of an explicit function relating the ion interaction coefficient to the ionic strength and the addition of a third virial coefficient to Eq. (5.83). For the case of an electrolyte MX the excess Gibbs energy is given by... 

FIGURE 15.10 Plots of the Gibbs free energy per unit area, AG/A, as a function of the distance between two oppositely charged planar surfaces, L, with the ionic strength as a parameter. The curves are calculated from Equation 15.63 with e=80, c =-0.16C/m, and Op = 0.03C/m. ... 

As we have seen in the preceding chapter, the standard thermodynamic properties of species in aqueous solutions are functions of ionic strength when they have electric charges. Substituting equation 3.6-3 for species j and for H + in equation 4.4-9 yields the standard transformed Gibbs energy of formation of species j as a function of pH and ionic strength at 298.15 K ... 

Table 4.1 Standard Transformed Gibbs Energies in kJ mol 1 of Hydrolysis of ATP as a Function of Temperature, pH, and Ionic Strength...

Table 4.4 Standard Transformed Reaction Gibbs Energies (in kJ mol1) for the Reactions of Glycolysis at 298.15 K and 0.25 M Ionic Strength...

The functions of pH and ionic strength that yield ArGj°, ArH °, and Ar/VH can also be used to plot these properties in terms of pH at a chosen ionic strength and in terms of ionic strength at a chosen pH. Figure 4.2 shows the dependence of the standard transformed Gibbs energy of the hydrolysis of ATP to ADP on pH. 

The amount of the oxygen component in the system is given by nc(O) = LN0(i)ni, where N0(i) is the number of oxygen atoms in reactant i. p 0(H2O) is the standard transformed chemical potential for H,0 at the specified pH and ionic strength. The standard further transformed Gibbs energy of formation of reactant i is given by... 

Table 6.2 Standard Transformed Gibbs Energies of Formation at 298.15 K, pH 7, and 0.25 M Ionic Strength, Standard Further Transformed Gibbs Energies of Formation at [ATP] = 10 4 M and [ADP] = 10 2 M, and Standard Further Transformed Gibbs Energies of Formation at [ATP] = 10 2 M and [ADP] = 10-2 M...

Table 6.3 Standard Further Transformed Gibbs Energies of Formation of C(, and C, at pH 7 Ionic Strength 0.25 M for Different Specified Concentrations of ATP...

Table 7.1 Standard Transformed Gibbs Energy of Formation AfG ° and Standard Further Transformed Gibbs Energies of Formation AfG ° of Hemoglobin Tetramer at 21.5JC, 1 bar, pH 7.4, [Cl ] = 0.2 M, and 0.2 M Ionic Strength...

Table 7.5 Standard Transformed Gibbs Energies of Formation for the Catalytic Site of Fumarase in kJ moF1 at 25 C and Ionic Strength 0.01 M...

Table 9.3 Standard Transformed Gibbs Energies (in kJ moE ) of Reactions and Standard Apparent Reduction Potentials (in volts) at 289.15 K, 1 bar, pH 7, and Ionic Strength 0.25 M for Reactions Involved in the Methane Monooxygenase Reaction...

Gibbs energy of formation of species j at specified T, P, and ionic strength (J mol-1)... 

---