The thermodynamic parameters were calculated. for the vapor-liquid equilibrium of “dimethylzinc-dimethyl selenide” system using the tensometric data obtained for high-purity dimethylzinc, dimethylselene and their equimolecular solution. For this purpose, the Wilson’s model, whose parameters were calculated by the activity coefficients of components in the azeotrope, were used. The calculation was made using the mathematical package MathCad 14. The parameters of the Wilson’s model allowed to calculate the activity coefficients, the vapor compositions, the partial pressures, the component separation coefficient, the excess functions for the solution, and to draw isothermal diagrams for vapor-liquid equilibrium. The table lists the calculated activity coefficients and the excess functions for the solution (HE, GE, kJ/mole).
The values of the activity coefficients (γi <1), the excess enthalpy of the solution (HE <0), and the shapes of isothermal P-X equilibrium diagrams indicate on the existence of an azeotrope in this system and the negative deviation of this solution from the ideal. The values of Gibbs excess energy for this solution (GE) in the whole range of concentrations and temperatures is negative, that indicates on the formation of homogeneous solutions. As the temperature rises, then excess enthalpy increases, that indicates a positive value of the heat capacity change in during the formation of the dimethylzinc-dimethyl selenіde solution. The deviation of this system from the Raoult’s law is explained, in our opinion, by the enthalpy factor. In the investigated solution, the energy of interaction between different molecules is greater than that between identical molecules. This indicates on significant difference between the parameters (l12 – l11) and (l12 – l22) in the Wilson’s equation.
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