An investigation of ion-pairing of alkali metal halides in aqueous solutions using the electrical conductivity and the Monte Carlo computer simulation methods

• Published in: Journal of molecular liquids Vol. 190; pp. 34 - 41
• Main Authors: Gujt, Jure, Bešter-Rogač, Marija, Hribar-Lee, Barbara
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01-02-2014
• Subjects: Alkali halides aqueous solutions; Association constant; Electric conductivity; Monte Carlo computer simulations; Water structure; Association constant; Water structure; Alkali halides aqueous solutions; Monte Carlo computer simulations; Electric conductivity; alkali halides aqueous solutions; association constant; water structure; electric conductivity
• ISSN: 0167-7322; 1873-3166
• DOI: 10.1016/j.molliq.2013.09.025

The ion pairing is, in very dilute aqueous solutions, of rather small importance for solution properties, which renders its precise quantification quite a laborious task. Here, we studied the ion pairing of alkali halides in water by using the precise electric conductivity measurements in dilute solutions, and in a wide temperature range. The low-concentration chemical model was used to analyze the experimental data, and to estimate the association constant of different alkali halide salts. It has been shown that the association constant is related to the solubility of salts in water and produces a ‘volcano relationship’, when plotted against the difference between the free energy of hydration of the corresponding individual ions. The computer simulation, using the simple MB+dipole water model, was used to interpret the results, to find a microscopic basis for Collins' law of matching water affinities.
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•We report precise conductance data and Ka for alkali halides that can be used to evaluate theoretical models.•Graph of Ka vs difference in ΔG of hydration of the corresponding individual ions produces a ‘volcano relationship’.•Association constant is interpreted using a simple solution model.