Entropy change of mixing

The entropy change of mixing for ideal gases is given by the equation following Eq. (11.26). For UNmixing of a binary mixture it becomes ... 

The Flory-Huggins lattice model assumes that a polymer chain consists of a number of equivalent segments. The extension to polymer solvent interactions assumes that the polymer solution consists of a three-dimensional lattice and each lattice site is occupied either by a polymer segment or by a solvent molecule. Flory and Huggins calculated the entropy change of mixing as... 

The above examples are related to the concept of the one-dimensional solubility parameter. However the effects of specific interactions between some functional groups can change compatibility of the system. ChloroaUcanes compared with esters are known to be better solvents for polymethylmethacrylate. Aromatic hydrocarbons although having solubility parameters much higher than those of alkanes, dissolve some rubbers at least as well as alkanes. Probably it is related to increase in entropy change of mixing that has a positive effect on solubility. 

As the mole fractions yi vary between 0 and 1, the entropy change of mixing for an ideal mixture is always different from zero and positive. 

As it can easily be seen, only As, Ag, and Aa are different from zero for an ideal mixture, which is caused by the entropy change of mixing. 

Estimates of entropy change of mixing can be made from APb, j. Information about APm, h is available from EOS theories discussed in Chapter 2. A cubic equation for TgS can be recognized from Equation (6.39). 

The entropic interaction parameter (Xs) is obtained from the partial molar excess entropy change of mixing (ASjexc) (not including the combinatorial part) ... 

Assume that 1.000 mol of dry air consists of0.780 mol of nitrogen, 0.210 mol of oxygen, and 0.010 mol of argon. Find the entropy change of mixing of 1.000 mol of dry air. Disregard the fact that each substance has more than one isotope. 

The isothermal enthalpy of mixing is the amount of heat we must add or subtract when we mix the species adiabat-ically and then heat or cool as needed to bring the mixture to its starting temperature. There is no direct experimental way to measure the isothermal entropy change of mixing we must infer it from other measurements. 

Estimate the isothermal entropy change of mixing for binary mixtures of two species for Xi =0.5, 0.3, 0.1 and 0.01, assuming ideal solution. 

Relate the volume, enthalpy, and entropy changes of mixing to the relative intermolecular interactions of like (A/) and unlike i-j) interactions. Define the enthalpy of solution. Calculate the enthalpy of mixing from the enthalpy of solution or vice versa. 

To find the intensive entropy change of mixing, we divide by the total number of moles ... 

However, there will be a positive entropy change of mixing, since the ideal gas mixture has more possible configurations (i.e., is more random) than the separated pure species. The expression for the entropy change of mixing of an ideal gas is given by Equation... 

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