Jamey K. Hovey

Thermodynamics of sulphuric acid: apparent and partial molar heat capacities and volumes of aqueous HSO–4 from 10–55 °C and calculation of the second dissociation constant to 350 °C

Apparent molar heat capacities and volumes of aqueous solutions containing H2SO4 have been determined from 10 to 55°C. These results are complicated by the presence of bisulphate and sulphate ions as well as effects due to chemical relaxation. Consideration of these contributions has led to derived standard-state partial molar heat capacities and volumes for HSO–4 over the stated temperature range. The heat capacity and volume data, which are related to Gibbs free energies by derivatives with respect to temperature and pressure, have been used along with a semi-theoretical model to calculate equilibrium constants for the dissociation of bisulphate to 350°C. Results of these calculations are in good agreement with the best equilibrium data presently available.

Apparent molar heat capacities and volumes of aqueous HClO4, HNO3, (CH3)4NOH and K2SO4 at 298.15 K

Abstract Apparent molar heat capacities and volumes of HClO 4 (aq), HNO 3 (aq), (CH 3 ) 4 NOH(aq) and K 2 SO 4 (aq) have been determined at 298.15 K. Infinite dilution standard state partial molar heat capacities and volumes have been calculated from these data. We recommend revised values for the conventional ionic partial molar heat capacities and volumes of ClO 4 − (aq), NO 3 − (aq) and SO 4 2− (aq).

Thermodynamics of aqueous uranyl ion: Apparent and partial molar heat capacities and volumes of aqueous uranyl perchlorate from 10 to 55°C

Abstract Apparent molar heat capacities and volumes of aqueous solutions containing UO2(ClO4)2 in dilute (≈0.06 molal) HClO4 have been determined from 10 to 55°C. These results have been analyzed using Youngs rule to obtain apparent molar volumes and heat capacities for the solute UO2(ClO42). The temperature dependences of the conventional standard-state heat capacity and volume functions for UO22+ (aq) are well represented by the following equations: V °/ cm ( 3 0 mo1 P-1) −80.94 + 0.6091 T - 0.001063T 2 and C / p 0 /( J K −1 mol −1 ) = 350.5 — 0.8722T — 5308/T —90) that are valid from 10 to 55°C. These results differ substantially from results of earlier measurements employing different uranyl salts. These differences are likely due to the presence of ion-paired or hydrolyzed U (VI) species in the earlier studies.

Thermodynamics of aqueous EDTA systems: apparent and partial molar heat capacities and volumes of aqueous strontium and barium EDTA

Apparent molar heat capacities and volumes have been determined for Na2SrEDTA (aq) and Na2BaEDTA (aq). Standard state partial molar heat capacities and volumes have been calculated as well as the partial molar properties at 0.1 m ionic strength that are needed for various thermodynamic calculations. Selected enthalpies and stability constants from the literature have been combined with out heat capacities to generate predicted stability constants to 200°C.

Apparent molar heat capacities and apparent molar volumes of Hg(ClO4)2(aq) and Pb(ClO4)2(aq) at 298.15 K

Abstract We have made calorimetric and densimetric measurements on aqueous solutions of Hg(ClO 4 ) 2 and Pb(ClO 4 ) 2 in dilute HClO 4 at 298.15 K. Results are expressed as “experimental” apparent molar heat capacities and apparent molar volumes, which include contributions from the aqueous metal perchlorate solutes and from the perchloric acid. We have used Youngs rule to assess and subtract the contribution of HClO 4 from these “experimental” apparent molar properties to yield apparent molar heat capacities and apparent molar volumes for (Hg 2+ + 2ClO 4 − )(aq) and (Pb 2+ + 2ClO 4 − )(aq). From these heat capacities and volumes we have calculated partial molar properties at infinite dilution for these metal perchlorate solutes. The partial molar heat capacities and partial molar volumes at infinite dilution were found to be −16 J · K −1 · mol −1 and −14.2 cm 3 · mol −1 for Hg 2+ (aq) and −56 J · K −1 · mol −1 and −17.8 cm 3 · mol −1 for Pb 2+ (aq), respectively. We have compared these values for Hg 2+ (aq) and Pb 2+ (aq) with those calculated from semi-empirical correlations.