Gibbs energy molecular interpretation

At specified concentration of molecular oxygen, the five forms of hemoglobin are pseudoisomers, and they have the same further transformed Gibbs energy of formation at equilibrium. The further transformed thermodynamic properties of the tetramer can be calculated from experimental measurements of the fractional saturation, but in order to interpret experimental data, it is necessary to provide for the partial dissociation of tetramer 02 Bz into dimers a/3 (3). Seven apparent equilibrium constants are required to describe experimental data, and it is shown that all seven can be determined using limiting forms (4). 

Sbhnel and Mullin, Garside and recently Barlow and Haymet have discussed the molecular Interpretation of induction times from the standpoint of classical nucleation theory. Crystal nuclei with a critical size must be formed before the new solid phase is visible. According to the model there exists a free energy barrier, AG to the formation of the crystal nuclei. AG is proportional to (InS), where S is the supersaturation ratio. The Gibb s free energy, AG of the supersaturated solution is equal to -RTlnS (R=gas constant T=temperature). The induction time is a function of AG and thus AG according to the following equation... 

Over a long period of time experimental results on amphiphilic monolayers were limited to surface pressure-area ( r-A) isotherms only. As described in sections 3.3 and 4, from tc[A) Isotherms, measured under various conditions, it is possible to obtain 2D-compressibilities, dilation moduli, thermal expansivities, and several thermodynamic characteristics, like the Gibbs and Helmholtz energy, the energy cmd entropy per unit area. In addition, from breaks in the r(A) curves phase transitions can in principle be localized. All this information has a phenomenological nature. For Instance, notions as common as liquid-expanded or liquid-condensed cannot be given a molecular Interpretation. To penetrate further into understanding monolayers at the molecular level a variety of additional experimental techniques is now available. We will discuss these in this section. 

The effectiveness of Wilson s model lies in the fact that only two parameters are required to describe the Gibbs energy at a given temperature. Its weakness lies in the fact that there is no clear molecular interpretation of these parameters. Wilson s approach works for a great variety of systems but when the departures from ideality are complex, more detailed models are required. Some extensions of Wilson s work have been discussed by Renon and Prausnitz [8] but they require introduction of more adjustable parameters. 

To obtain a physical interpretation for the residual Gibbs energy, we start with an ideal-gas mixture confined to a closed vessel. As the process, we consider the reversible isothermal-isobaric conversion of the ideal-gas molecules into real ones. Although this process is hypothetical, it is a mathematically well-defined operation in statistical mechanics the process amounts to a "turning on" of intermolecular forces. We first want to obtain an expression for the work, but since the process involves a change in molecular identities, we must start with the general energy balance (3.6.3). For a system with no inlets and no outlets, (3.6.3) becomes... 

Here, is the concentration (or solubility) of benzene in water, whereas Qa is the concentration of benzene in (almost) pure benzene. Clearly, the rhs of (4.196) is a measurable quantity. The Ihs of (4.196) is, according to the molecular interpretation, the change in Gibbs free energy for the transfer of a benzene molecule from a fixed position in pure water to a fixed position in (almost) pure benzene. Due to its local character, this quantity measures the difference in the solvation properties of benzene and water with respect to a single benzene molecule. ... 

This is a detailed review and evaluation of the enthalpies, Gibbs energies, entropies, and heat capacity changes accompanying ionization of organic acids. Included are eleven tables of data on various types of acids, including the carboxylic acids, phenols, anilinium ions, ammonium ions, the amino acids, barbituric acids, and several inorganic acids. The authors also discuss the interpretation of the data in terms of molecular considerations. The tabulated data refer to 25 "C and standard state conditions. There are 224 references. 

Figure 4.6 A graphical interpretation in terms of the Broensted-Polanyi correlations of variations in standard energy characteristics (the Gibbs potential) of participants of (A) reaction (4.85) and (B) catalytic process (4.3)- 4.4) with disperse active phase K and one thermalized molecular intermediate Ki. Sign / indicates the transition state TS in elementary reaction (4.85) /I and 2 relate to transition states TSq and TS2 in elementary reactions 1 and 2 of scheme (4.4).

Also in 1978, Beutier and Renon (PI) presented a slightly different interpretation of the Pltzer equation for use with solutions containing molecular solutes. Noting the additive form of the equation given by Pltzer for the excess Gibbs free energy ... 

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