Mixing, energy entropy

One practical example of demixing that might be attributed to a difference in crystallizability is the incompatibility in blends of polymers with different stereochemical compositions. The stereochemical isomers contain both chemical and geometrical similarities, but differ in the tendency of close packing. In this case, both the mixing energy B and the additional mixing entropy due to structural asymmetry between two kinds of monomers are small. However, the stereochemical differences between two polymers will result in a difference in the value of Ep. Under this consideration, most experimental observations on the compatibility of polymer blends with different stereochemical compositions [89-99] are tractable. For more details, we refer the reader to Ref. [86]. 

Using an automated film balance the behavior of mixed monomolecular films exhibiting deviations from ideality was studied. Particular attention was paid to condensation effects obtained when cholesterol is mixed with a more expanded component. The deviations at various film pressures are discussed in terms of the partial molecular areas of the film components. Slope changes in these plots are caused by phase transitions of the expanded monolayer component and do not indicate the formation of surface complexes. In addition, the excess free energies, entropies, and enthalpies of mixing were evaluated, but these parameters could be interpreted only for systems involving pure expanded components, for which it is clear that the observed condensation effects must involve molecular interactions. 

System with random fluxes is defined as the nonequilibrium system where the fluxes of substance, heat, etc. change randomly. One can cite numerous examples of such systems turbulent gas-liquid systems with intensive heat/mass transfer, turbulent fluids containing dispersed solids, etc. In the case of pore formation, such situation is realized when the heat fluxes change randomly because of air fluidization or mechanical mixing. All macroscopic measured parameters of stationary turbulent flows, like their pressure, temperature, excess (free) energy, entropy, etc. do not change with time, while their values and directions in different spots of the flows can vary significantly. 

Calculate the excess Gibbs energy, entropy, and enthalpy of mixing for the carbon tetrachloride-acetonitrile system discussed in questions 3 and 4. Prepare a plot of these data and compare the results with those obtained in the previous question. 

In this appendix, we discuss briefly the concept of free energy of mixing and entropy of mixing, and the relatively newly defined concept of assimilation. A more detailed discussion of this topic may be found elsewhere (Ben-Naim 1987a,b). 

AGmix free energy of mixing AHmix " heat of mixing ASmix entropy of mixing... 

By substituting expressions for AX (mix) fromEqs. 11.1.8-11.1.12 inEq. 11.1.13, we obtain the following expressions for the excess molar Gibbs energy, entropy, enthalpy, internal energy, and volume ... 

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