The Gibbs Free Energy of Solution

The Gibbs free energy of solution is the difference between the Gibbs free energy of solvation of the solute in the solvent and any Gibbs free energy of interaction in the pure solute that are lost on dissolution, if it is a solid, a liquid, or a nondilute gas. 

To perform calculations of phase equilibrium we must obtain expressions for the fugacity of component in solution. The key excess property here is the Gibbs free energy of solution. We begin by defining a new dimensionless property, the activity coefficient (yi) of component i in solution ... 

The Gibbs free energy of solution, AG, can be expressed by the sum of the Gibbs free energy for the cavity formation, G,., and the interaction free energy between solute and solvent molecules, Gji... 

Equation 5 shows how the Gibbs free energy of reaction varies with the activities (the partial pressures of gases or molarities of solutes) of the reactants and products. The expression for Q has the same form as the expression for K, but the activities refer to any stage of the reaction. 

If we were to place a piece of zinc metal into an aqueous copper(II) sulfate solution, we would see a layer of metallic copper begin to deposit on the surface of the zinc (see Fig. K.5). If we could watch the reaction at the atomic level, we would see that, as the reaction takes place, electrons are transferred from the Zn atoms to adjacent Cu2 r ions in the solution. These electrons reduce the Cu2+ ions to Cu atoms, which stick to the surface of the zinc or form a finely divided solid deposit in the beaker. The piece of zinc slowly disappears as its atoms give up electrons and form colorless Zn2+ ions that drift off into the solution. The Gibbs free energy of the system decreases as electrons are transferred and the reaction approaches equilibrium. However, although energy is released as heat, no electrical work is done. 

In the framework of the mobile order and disorder (MOD) theory five components contribute most to the Gibbs free energy of partitioning of a solute in a biphasic system of two essentially immiscible solvents [23] ... 

Here G is the Gibbs free energy of the system without external electrostatic potential, and qis refers to the energy contribution coming from the interaction of an apphed constant electrostatic potential s (which will be specified later) with the charge qt of the species. The first term on the right-hand side of (5.1) is the usual chemical potential /r,(T, Ci), which, for an ideal solution, is given by... 

In thermodynamic terms, solutes can be divided into two classes. For hydrophobic solutes in dilute solution in water, the partial Gibbs free energy of solution is positive. This is because water molecules that surround a less polar molecule in solution are more restricted in... 

All the solubilities so far mentioned have been presented in weight or concentration units. These may be converted via standard thermodynamic formulas into Gibbs free energies of solution. One group of authors, however, has preferred to present their data in this form, for YC13, LaClj, and six other lanthanide trichlorides (184). 

The total differential of the Gibbs Free Energy of B in solution (nBuB) is... 

Here, k is the Boltzmann constant (=. f / f ) is the Gibbs free energy of the whole solution and/t is the chemical potential of the solvent in solution. Moreover,... 

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