Nonpolar mixture

Siddiqi-Lucas suggested that component volume fractions might be used to correlate the effects of concentration dependence. They found an average absolute deviation of 4.5 percent for nonpolar-nonpolar mixtures, 16.5 percent for polar-nonpolar mixtures, and 10.8 percent for polar-polar mixtures. 

For nonpolar mixtures, the following equation gives mixture viscosity usually within 5 to 10% ... 

Polar + Nonpolar Mixtures Figure 7.3 summarizes Hi G= and for mixtures of acetonitrile with benzene at 318.15 K.2 The large positive H results principally from the energy that must be added to separate the highly polar acetonitrile molecules, (which are held together by strong (dipole + dipole)... 

In a GC experiment in which the liquid stationary phase is polar, which would have a shorter retention time—a nonpolar mixture component with a high vapor pressure or a polar mixture component with a low vapor pressure Explain. 

Use partition chromatography for highly polar mixtures and adsorption chromatography for very nonpolar mixtures. 

Explain why the order of elution of polar and nonpolar mixture components would be reversed when switching from normal phase to reverse phase. 

A nonpolar mixture component with a high vapor pressure would have the shorter retention time because both the high vapor pressure and the fact that it has a polarity different from the stationary phase means that it would likely be found in the mobile phase most of the time. 

In reverse phase chromatography, the polar mixture components would elute first since they would be attracted by the polar mobile phase and repelled by the nonpolar stationary phase. In normal phase chromatography, nonpolar mixture components would elute first since they would be attracted by the nonpolar mobile phase and repelled by the polar stationary phase. 

The Separated Associated Fluid Interaction Model for Polar + Nonpolar Mixtures... 

Two special applications of Eq. (86) should be mentioned, namely the calculation of isotopic diffusion and the calculation of the coefficient of diffusion for polar-nonpolar mixtures. For mixtures of heavy isotopes, Ma = MB = M, aK = = [Pg.188]

Mixtures approximating curve (2), in which the critical locus is almost linear, usually are formed when the components have similar critical properties and form very nearly ideal mixtures. A minimum in the critical locus, as in curve (3), occurs when positive deviations from Raoult s law occur that are fairly large, but do not result in a (liquid + liquid) phase separation. Some (polar + nonpolar) mixtures and (aromatic + aliphatic) mixtures show this type, of behavior. 

Nonpolar + Nonpolar mixtures Figure 17.3 summarizes the excess thermodynamic properties for (cyclohexane + hexane) mixtures.J 4 We have chosen this... 

Alkanes that we will use as examples in this section may have a small dipole moment. We may instead have appropriately titled this section as Almost (Nonpolar + Nonpolar) Mixtures . The mixtures we describe first are at ambient pressure p ss 0.1 MPa). Later we will describe the effect of pressure on the excess thermodynamic properties. 

Polar + Nonpolar Mixtures Figure 17.6 summarizes HC m, and for mixtures of 1-chlorobutane with heptane.9 We note that for this system is significantly larger than for any of the (nonpolar + nonpolar) systems described previously. A major contribution to H is the energy required to break apart the (dipole + dipole) interaction between the polar 1-chlorobutane molecules. Thus, if A-A represents (heptane + heptane) interactions and B-B represents (1-chlorobutane + 1-chlorobutane) interactions, with A-B representing (1-chlorobutane-I-heptane) interactions, then energy is required to break apart A-A that is not recovered when A-B forms, and H is positive. 

An analogy can be made with nonelectrolyte mixtures. For (nonpolar + nonpolar) mixtures, near-ideal solution behavior occurs and activity coefficients given by... 

Application of a Generalized van der Waals Equation of State to Several Nonpolar Mixtures at High Pressures... 

The ideal-gas law is a simplistic model that is applicable to simple molecules at low pressure and high temperature. As for Kay s method, which in general is superior to the others, it is basically suitable for nonpolar/nonpolar mixtures and some polar/polar mixtures, but not for nonpolar/polar ones. Its average error ranges from about 1 percent at low pressures to 5 percent at high pressures and to as much as 10 percent when near the critical pressure. 

Rathbun and Babb [20] suggested that Darkens equation could be improved by raising the thermodynamic correction factor PA to a power, n, less than unity. They looked at systems exhibiting negative deviations from Raoult s law and found n = 0.3. Furthermore, for polar-nonpolar mixtures, they found n = 0.6. In a separate study, Siddiqi and Lucas [22] followed those suggestions and found an average absolute error of 3.3 percent for nonpolar-nonpolar mixtures, 11.0 percent for polar-nonpolar mixtures, and 14.6 percent for polar-polar mixtures. Siddiqi, Krahn, and Lucas (ibid.) examined a few other mixtures and... 

The Weimer-Prausnitz (WP) Method (10). Starting with the Hilde-brand-Schatchard model for nonpolar mixtures (34), Weimer and Praus-... 

Liquid Mixtures Compositions at the liquid-vapor interface are not the same as in the bulk liquid, and so simple (bulk) composition-weighted averages of the pure-fluid values do not provide quantitative estimates of the surface tension at the vapor-liquid interface of a mixture. The behavior of aqueous mixtures is more difficult to correlate and estimate than that of nonpolar mixtures because small amounts of organic material can have a pronounced effect upon the surface concentrations and the resultant surface tension. These effects are usually modeled with thermodynamic methods that account for the activity coefficients. For example, a UNIFAC method [Suarez, J. T. C. Torres-Marchal, and P. Rasmussen, Chem. Eng. Set, 44 (1989) 782] is recommended and illustrated in PGL5. For nonaqueous systems the extension of the parachor method, used above for pure fluids, is a simple and reasonably effective method for estimating a for mixtures. 

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