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Abstract: Proceeding from the Clausius-Clapeyron equation, the relation is derived thatestablishes a correlation between the partial enthalpy of evaporation frombinary solutions, concentrations of components, and equilibrium vaporpressures. The difference between enthalpies of evaporation of components fromsolutions and those from the pure liquids, DDH, depends on the chemicalnature and concentrations, X, of solutions. The effect of concentrations onDDH makes different appearances in ideal and non-ideal solutions, although,as a whole, DDH increases with the growth of concentration of the secondcomponent. A model is introduced, which considers DDH as the sum of energeticchanges of three sequential stages: passage of molecules from the bulk liquidinto the surface layer, exit of the molecules on the outer side of theinterface, and the following desorption into the gas phase. In the framework ofthe model, the main contribution to enthalpy of evaporation comes from theprocesses in the surface layer. It is suggested that adsorption from solutions,which changes the chemical composition of the surface layer with respect tothat of the bulk solution, determines, to great extent, the difference in theforms of the curves DDH=fX for ideal and non-ideal solutions.



Autor: Vladimir Kh. Dobruskin

Fuente: https://arxiv.org/







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