Thermodynamic properties of alkali halides. II. Enthalpies of dilution and heat capacities in water at 25°C |
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Authors: | J. -L. Fortier P. -A. Leduc J. E. Desnoyers |
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Affiliation: | (1) Department of Chemistry, Université de Sherbrooke, Sherbrooke, Québec, Canada |
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Abstract: | The enthalpies of dilution and volumetric specific heats of most alkali halides were measured in water at 25°C with flow microcalorimeters in the concentration range 0.01 to 1m. Apparent molal relative enthalpiesL, derived from the enthalpies of dilution, can be represented by a parametric equation in molality. CombiningL with osmotic data, excess entropies can be calculated. Excess free energies, enthalpies, and entropies are compared at 0.5m, and the observed trends are consistent with a model of structural interactions in aqueous alkali halide solutions. The apparent molal heat capacitiesC were fitted with the equationC=C°+AC(d0m)1/2+BCm. TheC° are, in general, additive to better than 1 J-K–1-mole–1 and reflect mostly the structural part of ion-solvent interactions. TakingC°(H+)=0, conventional ionicC° are obtained. The parameterBCfor different pairs of ions follows approximately the same trends as the corresponding parameterBVfor apparent molal volumes and seems to reflect structural interactions between the ions. |
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Keywords: | Heat capacity enthalpy of dilution heat of dilution relative apparent molal enthalpy alkali halide water aqueous solution |
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