Thermodynamics of aqueous gallium chloride. Apparent molar volumes and heat capacities at 25°C |
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| Authors: | P F M van Gaans H A J Oonk G Somsen |
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| Institution: | (1) Institute of Earth Sciences, Department of Geochemistry, University of Utrecht, P. O. Box 80.021, 3508 TA Utrecht;(2) Faculty of Chemistry, Department of Chemical Thermodynamics, University of Utrecht, Padualaan 8, 3584 CH Utrecht;(3) Department of Chemistry, Vrije Universiteit, de Boelelaan 1083, 1081 HV Amsterdam |
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| Abstract: | Apparent molar volumes and heat capacities of aqueous GaCl3 have been measured at 25°C in binary GaCl3 solutions up to 3 mol-kg–1, and in ternary GaCl3-HCl solutions, containing 0.1345 mol-kg–1 HCl to suppress hydrolysis, up to a concentration of 1 mol-kg–1 GaCl3. Using the Pitzer interaction model for the excess properties, and using ridge regression for the derivation of physically meaningful regression parameters, the measurements yield the following results for the standard molar properties and Pitzer parameters at 25°C: V0(GaCl3)=12.85 cm3-mol–1;
0
v
(GaCl3)=1.10×10–4 kg-mol–1–J–1–cm–3;
v
1
(GaCl3)=2.12×10–3 kg–mol–1–J–1–cm3; Cv(GaCl3)=1.34×10–5 kg2–J–1–cm3; Vo(GaOHCl2)=13.84 cm3–mol–1; C
o
p
(GaCl3)=–480.8 J–K–1–mol–1;
J
0
(GaCl3)=–8.02×10–6 kg–mol–1–K–2;
J
1
(GaCl3)=0.73×10–4 kg–mol–1–K–2; CJ(GaCl3)=–2.52×10–6 kg2-mol–2-K–2; C
p
0
(GaOHCl2)=20.4 J-K–1-mol–1. The latter parameter has only mathematical significance, its physical meaning is unclear. Comparison of the present experimental results for the standard molar properties of Ga3+ with semi-empirical correlations casts doubt upon the general validity of these correlation methods for trivalent cations. |
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| Keywords: | Aqueous GaCl3 apparent molar volume heat capacity Pitzer model hydrolysis |
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