Standard Gibbs energy difference

Gibbs energy of activation A G (standard free energy of activation A G ) (Id mol-1) — The standard Gibbs energy difference between the -> transition state of a reaction (either an elementary reaction or a stepwise reaction) and the ground state of the reactants. It is calculated from the experimental rate constant k via the conventional form of the absolute reaction rate equation ... 

These parameters permit calculation of the standard Gibbs energy difference between the states of the protein. For a simple two-state transition of the type... 

The standard Gibbs energy of electrolyte transfer is then obtained as the difference AG° x ° = AG° ° - AG° x. To estabfish the absolute scale of the standard Gibbs energies of ion transfer or ion transfer potentials, an extrathermodynamic hypothesis must be introduced. For example, for the salt tetraphenylarsonium tetraphenyl-borate (TPAs TPB ) it is assumed that the standard Gibbs energies of transfer of its ions are equal. 

This dependence is fundamental for electrochemistry, but its key role for liquid-liquid interfaces was first recognized by Koryta [1-5,35]. The standard transfer energy of an ion from the aqueous phase to the nonaqueous phase, AGf J, denoted in abbreviated form by the symbol A"G is the difference of standard chemical potential of standard chemical potentials of the ions, i.e., of the standard Gibbs energies of solvation in both phases. 

It is important to notice that the standard Gibbs energy of transfer refers to the transfer from pure w to pure organic o. It is therefore different from the Gibbs energy of partition, which refers to the transfer between mutually saturated solvents. Nevertheless, in the case of solvents of low miscibility such as water-DCE or water-nitrobenzene, the transferred ion is practically not hydrated by water present in the organic phase, so that... 

The determination of the standard Gibbs energies of transfer and their importance for potential differences at the boundary between two immiscible electrolyte solutions are described in Sections 3.2.7 and 3.2.8. 

Complex formation between a metal ion and a macrocyclic ligand involves interaction between the ion, freed of its solvation shell, and dipoles inside the ligand cavity. The standard Gibbs energy for the formation of the complex, AGjv, is given by the difference between the standard Gibbs... 

An enzyme is a protein that acts as a catalyst, i.e. a compound that increases the rate of a reaction without modifying the overall standard Gibbs-energy change in the reaction. Many different biochemical reactions occur in cells however, without enzymes they would not happen on a useful time scale to sustain life8. 

All quantities in Eq. (12.6) are measurable The concentrations can be determined by titration, and the combination of chemical potentials in the exponent is the standard Gibbs energy of transfer of the salt, which is measurable, just like the mean ionic activity coefficients, because they refer to an uncharged species. In contrast, the difference in the inner potential is not measurable, and neither are the individual ionic chemical potentials and activity coefficients that appear on the right-hand side of Eq. (12.3). 

Although the inner potential difference is not measurable in principle, it would be useful to have at least good estimates. We can see from Eq. (12.3) that this problem is equivalent to determining the difference in the chemical potential of individual ions. If we knew the standard Gibbs energies of transfer of the ions ... 

Therefore the determination of the standard Gibbs energies of adsorption at various symmetrical or unsymmetrical standard states leads directly to derivation of the particle-particle interaction parameter. The same result may be obtained from the difference of AG"" values calculated at zero surface coverage (0 = 0) and at saturated surface coverage (0=1), using Eqs. (30a) and (30b). 

The values of the standard Gibbs energy between nitrobenzene and water and the values of the standard potential differences between these two solvents for various ions are given in table 2.1. Equations (2.2.8) and (2.2.10) can be generalized readily for an electrolyte of any type of charge. 

It is worthwhile to compare the stability differences of the analogous hydrindanes and decalins. In both cases, the Gibbs standard free energy differences favor the trans isomers, by 1.3 kJ mol" in the hydrindanes and by about 10 kJ mol in the decalins (94MI3). This direction of the difference is in contrast with that found for the 1,3-heteroanalogs of cis- and trans-hydrindane. 

The assumptions of the special model of a nonuniform surface were formulated above in terms of changes of the standard Gibbs energy, AG°, and the Gibbs activation energy, AG. It can be assumed that standard entropy, S°, of each kind of adsorbed particles and activated complexes on different sites of a nonuniform surface does not differ substantially in this case there can be given practically equivalent formulation of the model... 

Let us consider now the case (47) when there are molecules of two different gases on the surface, the ability to be adsorbed not differing greatly for the two kinds of molecules we shall make use of Assumption 3 formulated in Section IX (i.e., assume that the change in the standard Gibbs energy of adsorption at passing from one surface site to another is the same for both kinds of molecules). 

The molar Gibbs energy of micelle formation is the Gibbs energy difference between a mole of monomers in micelles and the standard chemical potential in dilute solution ... 

Gibbs energy of ion and dipole transfer — The standard -> Gibbs energy of ion transfer (see also -> ion transfer at liquid-liquid interfaces) can be represented as the difference of two -> solvation energies A Gf = A acGA -... 

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