Standard Gibbs free energy of transfer

Standard Gibbs Free Energy of Transfer of n-Bu4NBr from Water to Water-Organic Solvent Mixtures as Deduced from Precise Vapor Pressure Measurements at 298.15°K... 

AGt° is the standard Gibbs free energy of transfer of the ionic surfactant between water and the solvent s AG °mlc is the same quantity defined between a micelle in water and in solvent s. 

Figure I. Single-ion standard Gibbs free energy of transfer from water to water + acetone mixtures based on S.F.T. calculations for the tetrabutylammonium ion (mole-fraction...

The standard potential of transfer for an individual ion, A cp , is not amenable to thermodynamic measurement. Its value can be determined by measuring the distribution ratio of its salt, for which the Gibbs free energy of transfer of the counterion is already known. From the experimentally accessible partition coefficient of the salt, the standard Gibbs free energy of transfer of the salt, AG aI7P, from phase a to phase p is calculated as... 

From the knowledge of K, it is possible to get the standard Gibbs free energy of transfer of alkanol from the organic phase to the interphase. The is essentially an equilibrium constant, and, therefore, the free energy of transfer of alkanol from oil to the interphase (AOp is... 

In principle, Gibbs free energies of transfer for trihalides can be obtained from solubilities in water and in nonaqueous or mixed aqueous solutions. However, there are two major obstacles here. The first is the prevalence of hydrates and solvates. This may complicate the calculation of AGtr(LnX3) values, for application of the standard formula connecting AGt, with solubilities requires that the composition of the solid phase be the same in equilibrium with the two solvent media in question. The other major hurdle is that solubilities of the trichlorides, tribromides, and triiodides in water are so high that knowledge of activity coefficients, which indeed are known to be far from unity 4b), is essential (201). These can, indeed, be measured, but such measurements require much time, care, and patience. 

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-... 

The product, —AF0F, in which A 0 is the difference of any two of these standard potentials, is the Gibbs free energy of transfer of hydrogen chloride, at infinite dilution, from one solvent to another. 

TABLE 1 Standard Gibbs Free Energies for Transfers (AG]() of Various Ions from Aqueous (W) to Nitrobenzene (NB) or 1,2-Dichloroethane (DCE) Phases... 

Hence, the difference of the standard Galvani potentials of the two phases is related to the standard Gibbs free energy of ion transfer ... 

A vac G j" = —ff—, where A " is the standard potential for transfer of ion i from a to f phase. If two immiscible liquids a and [i are mutually saturated, a certain amount of one solvent will be dissolved in the other solvent and vice versa. The corresponding energy of Gibbs free energy of ion transfer between two mutually balanced solvents is called the free partition energy. The main contributions to the energy of ion or dipole transfer between two solvent phases are (i) electrostatic - polarization of the medium (ii) production in a medium of a cavity to accommodate the ion or dipole also known as the solvo-... 

It is a serious drawback that it is not possible to determine the transfer activity coefficient of the proton (or of any other single-ion species) directly by thermodynamic methods, because only the values for both the proton and its counterion are obtained. Therefore, approximation methods are used to separate the medium effect on the proton. One is based on the simple sphere-in-continuum model of Born, calculating the electrostatic contribution of the Gibb s free energy of transfer. This approach is clearly too weak, because it does not consider solvation effects. Different ex-trathermodynamic approximation methods, unfortunately, lead not only to different values of the medium effect but also to different signs in some cases. Some examples are given in the following log yH+ for methanol -1-1.7 (standard deviation 0.4) ethanol -1-2.5 (1.8), n-butanol -t-2.3 (2.0), dimethyl sulfoxide -3.6 (2.0), acetonitrile -1-4.3 (1.5), formic acid -1-7.9 (1.7), NH3 -16. From these data, it can be seen that methanol has about the same basicity as water the other alcohols are less basic, as is acetonitrile. Di-... 

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