Relationship between the Structural State of Water and the Character of Ion Hydration in Concentrated 1:1 Aqueous Solutions of Electrolytes in Extreme Conditions

Abstract

It is suggested that the association parameter A be used as an indicator demonstrating the effect of extremal conditions on the structure of water in the series of solutions $LiCl{\kern 1pt} \to {\kern 1pt} NaCl{\kern 1pt} \to {\kern 1pt} KCl$. Analysis of the diagrams “A parameter–external conditions” permitted us to establish that compression has a weak effect on association of water molecules in the systems, in which case the effect of the ion field on the mutual ordering of solvent molecules does not change. In conditions of strong compression in NaCl–H₂O, positive hydration of Na⁺ changes to negative. On the contrary, at elevated temperatures, the probability of association of bulk water molecules increases and the effect of ions on the structure of the solvent decreases. Positive hydration of Li⁺ and negative hydration of K⁺ become less pronounced, and Na⁺ has no ordering effect on the structure of the solvent any longer.