The Thermodynamic Properties of Solutions

The formalism of the thermodynamics of solutions was described in Chapter 3. In this chapter we shall revisit the topic of solutions and apply statistical mechanics to relate the thermodynamic properties of solutions to atomistic models for their structure. Although we will not give a rigorous presentation of the methods of statistical mechanics, we need some elements of the theory as a background for the solution models to be treated. These elements of the theory are presented in Section 9.1. 

Work Is presently under way to extend the above model so as to extract from the experimental data the relevant parameters from a least-squares analysis (13). This model should be applicable to non-lonlc and Ionic systems. In the latter case, an extra term Is required to account for the shift In the CMC of solute 2 due to the sal-tlng-out of the monomers of 2 by solute 3 (7 ). The model In Its present form can still be used to estimate the thermodynamic properties of solute 3 In the micelle of surfactant 2 by adjusting the parameters to get a good fit with the experimental data. 

The main topics of interest are the molecular dimensions in solution, and their relation to intrinsic viscosity, and the thermodynamic properties of solutions. 

The possibility of predicting thermodynamic properties of redox couples and solutes in different solvents is very important. It should be very useful to develop procedures of transferring thermodynamic data such as redox potentials from solvent to solvent. In fact, the correlation found between kinetic and thermodynamic parameters of reactions in solutions, and solvent parameters such as DN, AN, dielectric constant, etc., indicates that it may be quite feasible to draw empirical formulas which predict, for instance, redox potentials in some solvents, based on well-established data obtained experimentally with other solvents. Thus, it may be possible to define transfer parameters (AG , AH , ASf, etc.) reflecting the difference between aqueous and polar aprotic solutions in the thermodynamic properties of solutes. 

Two additional observations should be made. First, the methods used here treat each of the ionic types as a separate species that influences the thermodynamic properties of solutions very strongly by virtue of its associated charge. Second, it is instructive to examine the dependence of the mean molal activity coefficient for several different electrolytes as a function of the molality. Representative examples are shown in Fig. 4.3.1. One sees at first a very steep drop in as m is increased, and then either a gradual or a very sharp... 

Corneliussen, R. Rice, S. A. Yamakawa, H., "On the Thermodynamic Properties of Solutions of Polar Polymers. A Comparison of Experiment and Theory," J. Chem. Phys., 38, 1768 (1963). 

Walther J. V. and Orville P. M. (1983) The extraction-quench technique for determination of the thermodynamic properties of solute complexes. Application to quartz solubility in fluid mixtures. Am. Mineral. 68, 731-741. 

Acceleration of some chemical reactions is possible when high-pressure techniques are employed. The effects on a given reaction can be predicted to a certain extent because the thermodynamic properties of solutions are well known. The rate of a reaction can be expressed in terms of the activation volume,... 

We shall make further use of this model in chap. XXV, when discussing the relationship between the thermodynamic properties of solutions and intermolecular forces. 

These authors note the importance of geometric packing for the thermodynamic properties of solutions. Indeed, since rigidity affects packing and thus distances between interacting units... 

This is a study of the thermodynamic properties of solutions of the actinides and some fission products in liquid bismuth. For dissolution of thorium, the cell... 

In the next section we shall discuss the physical properties and structure of the more important of the organic solvents mentioned in later chapters. In Chapter 2, the thermodynamic properties of solutions are discussed. Firstly, C. M. Criss discusses solubility and calorimetric measurements. In planning new work with unfamiliar solvents the extent of solubility of compounds is a primary consideration. Viscosity is also considered under this heading since although it is a transport property it is often used in the same way as thermodynamic measurements, to infer structural properties. An important technique for obtaining thermodynamic quantities of certain solutions is cryoscopy, the measurement of freezing point depressions, and this is discussed by R. Garnsey and J. E. Prue. Measurement of the e.m.f.s of suitable cells... 

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