Changes in Apparent Molar Water Volume and DKP Solubility Yield Insights on the Hofmeister Effect

This study examines the properties of a 4 × 2 matrix of aqueous cations and anions at concentrations up to 8.0 M. The apparent molar water volume, as calculated by subtracting the mass and volume of the ions from the corresponding solution density, was found to exceed the molar volume of ice in many...

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Bibliographic Details
Published in:The journal of physical chemistry. B 2011-12, Vol.115 (49), p.14784-14788
Main Authors: Payumo, Alexander Y, Huijon, R. Michael, Mansfield, Deauna D, Belk, Laurel M, Bui, Annie K, Knight, Anne E, Eggers, Daryl K
Format: Article
Language:English
Subjects:
Anions
Anions - chemistry
B: Biophysical Chemistry
Cations
Cations - chemistry
Density
Diketopiperazines - chemistry
Electrolytes
Free energy
Mathematical models
Solubility
Solvents
Thermodynamics
Water - chemistry
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Summary:This study examines the properties of a 4 × 2 matrix of aqueous cations and anions at concentrations up to 8.0 M. The apparent molar water volume, as calculated by subtracting the mass and volume of the ions from the corresponding solution density, was found to exceed the molar volume of ice in many concentrated electrolyte solutions, underscoring the nonideal behavior of these systems. The solvent properties of water were also analyzed by measuring the solubility of diketopiperazine (DKP) in 2.000 M salt solutions prepared from the same ion combinations. Solution rankings for DKP solubility were found to parallel the Hofmeister series for both cations and anions, whereas molar water volume concurred with the cation series only. The results are discussed within the framework of a desolvation energy model that attributes solute-specific changes in equilibria to solute-dependent changes in the free energy of bulk water.
ISSN:1520-6106
1520-5207
DOI:10.1021/jp206486z