Thermodynamics of the isotopic effects of the structural changes in water, associated with the hydration of the ions of the elements of subgroups IA, IIA, and VIIA at different temperatures

Abstract

ASsr,lin H20 and D20 and for the isotopic effects 6ASSr,i for the ions. It has been found that in the case of D20 there is more rapid temperature breakdown of the structure of water, compared with ordinary water. Numerical values have been obtained for the limiting temperatures for the existence of negative hydration of the ions Tli m in heavy water and for the isotopic effects ~Tlim. It has been concluded that 6Tlim, like Tlim, can be used as a quantitative characteristic of the short-range hydration of ions. The ions can be divided into three groups, according to the sign of 6Tlim: ~Tli m > 0, 6Tli m < O, ~Tli m = O. The phenomenon of the negative hydration of ions, discovered by Samoilov, has been confirmed. In [i], previously developed methods [2] were used to find the entropy characteristics of the structural changes in the solvent in the hydration of stoichiometric mixtures of the ions of the elements of subgroups IA, IIA, and VIIA in ordinary and heavy water at different temperatures. The study of the structural changes in water associated with the hydration of individual ions is of considerable interest. As shown in [2], this can be done by studying the values of AS~r,i -- the changes in the entropy of water associated with its structural changes in the region corresponding to the short-range hydration of ions, and also the isotopic effects in these quantities ~AS~r,i [3].