Standard molar Gibbs free energy

To find a numerical value for AHi, we need to know ArH° at one temperature, while evaluation of I requires ArG° at one temperature. The usual choice is to obtain ArH° and ArG° at T = 298.15 K from standard molar enthalpies of formation and standard molar Gibbs free energies of formation. Earlier in this chapter we referred to examples of these quantities. It is now time to define AfH° and AfG° explicitly and describe methods for their measurement. 

Standard molar enthalpies of formation, AfH°m, and standard molar Gibbs free energies of formation, Af(7, are useful, since they can be used to calculate ArH° and ArG°. The relationships are... 

Table 2.4 Crystal Ionic Radii and Standard Molar Gibbs Free Energies of Flydration of Ions... 

The standard molar Gibbs free energy of solution is ... 

Knowing the standard molar Gibbs free energy values and giving an initial mole number vector the determination of the equilibrium composition consists of minimizing (2.72) subject to the linear constraints (2.73). The direct application of (2.69-2.70), however, would be rather complicated. In the... 

The compilation (Lias et al. 1988) is also the source of most of the data for the gas phase acidity, AGa in kJ mol 1 at 298 K. This is the standard molar Gibbs free energy of proton dissociation according to S(H) — S + H+ in the gas phase. Again, the equilibrium constant of a competition reaction,... 

For purely electrostatic solute/solvent interactions, the Kirkwood equation, Eq. (4-27) [56], is applicable, which relates the standard molar Gibbs free energy of transfer of spherical dipolar molecules of radius r and dipole moment // from the gas phase (fir = 1) to a continuous medium of relative permittivity r-... 

Equation 8.2 obviously defines the general thermodynamic condition for the crystallization of solids. The equilibrium constant provides the key to calculate the standard molar Gibbs free energy for the process ... 

COM/PRA] Comert, H., Pratt, J. N., The standard molar Gibbs free energy of formation of NiO from high-temperature e.m.f. measurements, J. Chem. Thermodyn., 16, (1984), 1145-1148. Cited on pages 105, 401. 

Determination of the standard molar Gibbs free energies of formation of the silicates of cobalt and nickel by solid-state galvanic cells involving the CaF2-based composite electrolyte, J. Chem. Thermodyn., 32, (2000), 931-935. Cited on pages 243, 244,437. 

The standard states correspond to a hypothetical ideal gas at atmospheric pressure (101,325 Pa) and a hypothetical ideal 1 M aqueous solution. The standard molar Gibbs free energy, enthalpy, and entropy changes for the above reaction are donated by symbols AG°, AH°. and AS°, respectively. 

The symbol for standard molar Gibbs free energy of formation is AG . The units are kj mol ... 

Table 23.2 shows some values for some standard molar Gibbs free energy changes of formation. 

Table 23.2 Standard molar Gibbs free energy changes of some solids, liquids, gases and aqueous ions. The states are shown as state symbols after each substance.

---