Standard state heat capacities of aqueous electrolytes and some related undissociated species

Abstract

Uses of heat capacities of solutions of electrolytes are reviewed, with a particular emphasis on the standard state partial molar heat capacities and their applications to calculations of the effects of temperature on equilibrium constants, electrode potentials, enthalpies, and entropies. Methods of obtaining these standard partial molar heat capacities are summarized, followed by comparisons of values obtained in different ways. Many of the "best" such heat capacities are collected and then used as the basis for establishing single-ion heat capacities based on the convention that c p O (~+ ) = 0, followed by illustrations of the convenient use of these quantities. Finally, there is brief discussion of theoretical analysis of these standard partial molar heat capacities in relation to ion-solvent interactions.Key words: heat capacities, electrolytes; aqueous solutions, heat capacities; thermodynamics, electrolytes.RCsumC : On prksente une revue de l'utilisation des capacitCs calorifiques de solutions d'Clectrolytes en insistant d'une faqon particuliere sur les capacites calorifiques molaires partielles dans 1'Ctat standard et leurs applications aux calculs des effets de la temperature sur les constantes d'equilibre, les potentiels d'klectrode, les enthalpies et les entropies. On rksume les methodes d'obtenir ces capacites calorifiques molaires partielles standard et on prksente ensuite un comparaison des diverses valeurs obtenues d'aprks les diverses manieres. Plusieurs des ccmeilleuresa propriCtCs, comme les capacitks calorifiques, ont CtC rassemblCes et ont ensuite Ct C utilisees comme base pour I'Ctablissement des capacitks calorifiques d'un seul ion en se basant sur la convention que c,' (H+) = 0; elles sont suivies par des illustrations sur l'utilisation commode de ces quantitks. Enfin, on presente une breve discussion de I'analyse thiorique de ces capacitks calorifiques molaires partielles standard en relation avec les interactions ion-solvant.

Thermodynamic Properties and Phase Equilibria in the H2O–Ca(NO3)2 System

“…Calculated lines: blue  , this study; black  , ref ; red , ref . Symbols: ○, ref △, ref □, refs and .…”

“…The most correct approach to determine the contributions of individual species is the joint processing of data on heat capacities of various compounds containing them. It has been carried out for Ca 2+ and NO 3 – ions by a number of authors; − however, their results are usually limited to 298.15 K. An exception is the HKF EoS, which is used to describe and predict the standard state thermodynamic properties of aqueous species over a wide temperature range. It was shown that the values of C̅ p ,2 ° at high temperatures, predicted by the HKF EoS based on the data at moderate temperatures, are in good agreement with experiment.…”

“…The value of the standard partial molar heat capacity ( C̅ p ,2 ° ) of calcium nitrate at 298.15 K was estimated by various authors, − but in the present work, we considered the value of C̅ p ,2 ° as a variable parameter.…”

Heat Capacities and Volumes of Aqueous Dicarboxylate Salt Solutions of Relevance to the Bayer Process

“…9,10 The agreement is close to the likely limits of uncertainty of (1 to 2) J‚K -1 ‚mol -1 in C pφ . 11 Thus correction for heat losses in the calorimeter was considered unnecessary.…”

Standard molar volumes and heat capacities of aqueous solutions of sodium trifluoromethanesulfonate at temperatures up to 573K and pressures to 28MPa

“…The last term on the righthand side is the so-called relaxation term [27], accounting for the thermal shift associated with the change in equilibrium composition during the measurement of the solution heat capacity. The degree of association was calculated again from the thermodynamic association constant and activity coefficient models reported by Simonson et al [24] and term ð@a=@TÞ p was evaluated numerically.…”