Journal article
Cation Hydration and Ion Pairing in Aqueous Solutions of MgCl2 and CaCl2
The Journal of Physical Chemistry B, Vol.123(4), pp.891-900
2019
Abstract
Broadband dielectric relaxation spectroscopy (DRS) has been used to investigate aqueous solutions of MgCl2 and CaCl2 up to concentrations of about 1.8 mol L-1 at 25 °C over the frequency range 0.07 ≤ /GHz ≤ 89. Detailed analysis of the dominant solvent mode centered at ∼20 GHz showed that both Mg2+ and Ca2+ are strongly solvated, each immobilizing ∼20 water molecules on the DRS timescale. This is consistent with the formation of two well-defined hydration layers around both cations. The hydration shell of Ca2+(aq) was found to be slightly more labile compared with Mg2+(aq). Two or three low-intensity solute-related modes were observed at frequencies 10 GHz for MgCl2(aq) and CaCl2, respectively. Two of these modes were attributed to the formation of double-solvent-separated and solvent-shared 1:1 ion pairs. The third mode (observed at very low frequencies and only for some CaCl2 solutions) was thought to be due to an ion-cloud relaxation. No evidence was found for "slow" water or, consistent with the strong cation hydration, for contact ion pairs. The overall association constants for MgCl+(aq) and CaCl+(aq) calculated from the ion-pairing constants were very small but in good agreement with literature values obtained from other techniques.
Details
- Title
- Cation Hydration and Ion Pairing in Aqueous Solutions of MgCl2 and CaCl2
- Authors/Creators
- S. Friesen (Author/Creator) - University of RegensburgG. Hefter (Author/Creator) - Murdoch UniversityR. Buchner (Author/Creator) - University of Regensburg
- Publication Details
- The Journal of Physical Chemistry B, Vol.123(4), pp.891-900
- Publisher
- American Chemical Society
- Identifiers
- 991005541194207891
- Copyright
- © 2019 American Chemical Society
- Murdoch Affiliation
- School of Engineering and Information Technology
- Language
- English
- Resource Type
- Journal article
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- Collaboration types
- Domestic collaboration
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- Citation topics
- 2 Chemistry
- 2.89 Ionic, Molecular & Complex Liquids
- 2.89.677 Liquid Water
- Web Of Science research areas
- Chemistry, Physical
- ESI research areas
- Chemistry