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

1996 ◽  
Vol 74 (5) ◽  
pp. 639-649 ◽  
Author(s):  
Loren G. Hepler ◽  
Jamey K. Hovey
Keyword(s):  
Theoretical Analysis ◽  
Equilibrium Constants ◽  
Heat Capacities ◽  
Aqueous Electrolytes ◽  
Standard State ◽  
Solvent Interactions ◽  
Partial Molar Heat Capacities ◽  
Electrode Potentials ◽  
Solutions Of Electrolytes ◽  
Effects Of Temperature

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 CpO(H+) = 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.

Apparent molar heat capacities and volumes of some aqueous solutions of aliphatic amino acids at 288.15, 298.15, 313.15, and 328.15 K

1994 ◽  
Vol 72 (2) ◽  
pp. 362-368 ◽  
Author(s):  
Andrew W. Hakin ◽  
Michelle M. Duke ◽  
Sheri A. Klassen ◽  
Robert M. McKay ◽  
Kathryn E. Preuss
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Aqueous Solutions ◽  
Equilibrium Constants ◽  
Heat Capacities ◽  
Apparent Molar Volumes ◽  
Protein Chemistry ◽  
Standard State ◽  
Apparent Molar Heat Capacities ◽  
Molar Volumes

The thermodynamics of amino acid systems are key to the understanding of protein chemistry. We have found that many previous studies of the apparent molar volumes and heat capacities of aqueous solutions of amino acids were conducted at the standard temperature of 298.15 K. This does not allow for the fact that most biological processes occur at temperatures removed from this standard condition.In an attempt to address this imbalance we have measured densities and heat capacities for aqueous solutions of glycine, L-alanine, L-serine, and L-threonine at 288.15, 298.15, 313.15, and 328.15 K using a Picker flow microcalorimeter. Apparent molar volumes and heat capacities, and the associated standard state partial molar properties have been calculated. Constant pressure variations of revised Helgeson, Kirkham, and Flowers equations have been fitted to calculated standard state volumes and heat capacities over the temperature range 288.15 to 328.15 K. These equations may be used to estimate standard state volumes and heat capacities, and hence equilibrium constants, for aqueous amino acid systems at higher temperatures.

Thermodynamics of aqueous EDTA systems: Apparent and partial molar heat capacities and volumes of aqueous EDTA4−, HEDTA3−, H2EDTA2−, NaEDTA3−, and KEDTA3− at 25 °C. Relaxation effects in mixed aqueous electrolyte solutions and calculations of temperature dependent equilibrium constants

1988 ◽  
Vol 66 (4) ◽  
pp. 881-896 ◽  
Author(s):  
Jamey K. Hovey ◽  
Loren G. Hepler ◽  
Peter R. Tremaine
Keyword(s):  
Equilibrium Constants ◽  
Interaction Model ◽  
Electrolyte Solutions ◽  
Heat Capacities ◽  
Mixed Electrolytes ◽  
Temperature Dependent ◽  
Apparent Molar Heat Capacities ◽  
Partial Molar Heat Capacities ◽  
Relaxation Effects ◽  
Young's Rule

Calorimetric and densimetric measurements have led to apparent molar heat capacities and volumes for aqueous solutions of the mixed electrolytes [(CH3)4N]4EDTA + (CH3)4NOH, Na4EDTA + NaOH, and K4EDTA + KOH, and single electrolytes Na2H2EDTA and [(CH3)4N]3[HEDTA] at 25 °C. We have analyzed these results in terms of Young's rule and Pitzer's ion interaction model to obtain standard state partial molar heat capacities and volumes of EDTA4−(aq), HEDTA3−(aq), H2EDTA2−(aq), NaEDTA3−(aq), and KEDTA3−(aq) at 25 °C. For these calculations it was also necessary to evaluate the "relaxation" contribution to the measured heat capacities of some solutions. The partial molar heat capacities obtained here have been used with enthalpies from previous investigations for calculations of several equilibrium constants over wide ranges of temperature; volumes can be used for similar calculations of the effects of pressure.

Apparent molar heat capacities and volumes of unsaturated heterocyclic solutes in aqueous solution at 25 °C

1980 ◽  
Vol 58 (7) ◽  
pp. 704-707 ◽  
Author(s):  
Octavian Enea ◽  
Carmel Jolicoeur ◽  
Loren G. Hepler
Keyword(s):  
Aqueous Solution ◽  
Aqueous Solutions ◽  
Heterocyclic Compounds ◽  
Infinite Dilution ◽  
Heat Capacities ◽  
Group Additivity ◽  
Standard State ◽  
Apparent Molar Heat Capacities ◽  
Partial Molar Heat Capacities

Measurements at 25 °C with flow calorimeters and densimeters have led to heat capacities and densities of aqueous solutions of 15 unsaturated heterocyclic compounds containing nitrogen. From the results of these measurements we have obtained apparent molar heat capacities and volumes of the solutes. Extrapolations to infinite dilution have led to corresponding standard state apparent and partial molar heat capacities and volumes, which have been analyzed in terms of atomic and group additivity relationships.

Apparent and partial molar heat capacities and volumes of aqueous HClO4 and HNO3 from 10 to 55 °C

1989 ◽  
Vol 67 (9) ◽  
pp. 1489-1495 ◽  
Author(s):  
Jamey K. Hovey ◽  
Loren G. Hepler
Keyword(s):  
Nitric Acid ◽  
Aqueous Solutions ◽  
Perchloric Acid ◽  
Ionic Species ◽  
Heat Capacities ◽  
Standard State ◽  
Apparent Molar Heat Capacities ◽  
Solvent Interaction ◽  
Partial Molar Heat Capacities ◽  
Temperature Dependences

Apparent molar heat capacities and volumes of aqueous solutions containing HClO4 and HNO3 have been determined from 10 to 55 °C. The temperature dependences of the standard state heat capacities and volumes of ClO4− (aq) and NO3− (aq) from 10 to 55 °C were found to be well represented by the following equations:[Formula: see text]Combination of the experimental results with semiempirical equations for ion–solvent interaction has led to predictions of the standard state volumes and heat capacities for these ionic species at higher temperatures. Keywords: heat capacities, volumes, nitric acid, perchloric acid.

Apparent molar heat capacities and volumes of aqueous electrolytes at 25 °C: Cr(NO3)3, LaCl3, K3Fe(CN)6, and K4Fe(CN)6

1979 ◽  
Vol 57 (21) ◽  
pp. 2798-2803 ◽  
Author(s):  
Jan J. Spitzer ◽  
Inger V. Olofsson ◽  
Prem Paul Singh ◽  
Loren G. Hepler
Keyword(s):  
Aqueous Solutions ◽  
Infinite Dilution ◽  
Heat Capacities ◽  
Aqueous Electrolytes ◽  
Standard State ◽  
Apparent Molar Heat Capacities ◽  
Molar Volumes ◽  
High Charge ◽  
Flow Calorimeter ◽  
Partial Molar Properties

We have used a flow calorimeter and a flow densimeter for measurements at 25 °C of heat capacities and densities of aqueous solutions of four electrolytes of high charge type: LaCl3, Cr(NO3)3, K3Fe(CN)6, and K4Fe(CN)6. Results of these measurements have been used for calculating corresponding apparent molar heat capacities and apparent molar volumes, which have been extrapolated to infinite dilution to obtain the corresponding standard state apparent molar and partial molar properties. Uncertainties resulting from extrapolations of heat capacities are discussed. Results of our measurements are compared with those of earlier related investigations.

Apparent molar heat capacities and volumes of aqueous electrolytes at 25 °C: Na2SO4, K2SO4, Na2S2O3, Na2S2O8, K2S2O8, K2CrO4, Na2MoO4, and Na2WO4

1978 ◽  
Vol 56 (14) ◽  
pp. 1871-1873 ◽  
Author(s):  
Inger V. Olofsson ◽  
Jan J. Spitzer ◽  
Loren G. Hepler
Keyword(s):  
Aqueous Solutions ◽  
Infinite Dilution ◽  
Heat Capacities ◽  
Aqueous Electrolytes ◽  
Standard State ◽  
Apparent Molar Heat Capacities ◽  
Density Measurements ◽  
Dilute Aqueous Solutions

We have made beat capacity and density measurements leading to apparent molar beat capacities and volumes for dilute aqueous solutions of Na2SO4, K2SO4, Na2S2O3, Na2S2O8, K2S2O8, K2CrO4, Na2MoO4, and Na2WO4. We have used these apparent molar quantifies to extrapolate to infinite dilution to obtain the corresponding standard state apparent and partial molar quantities. These latter values have been used in calculation of conventional ionic beat capacities and volumes.

Apparent molar heat capacities and volumes of aqueous electrolytes at 25°C: NaIO3, KMnO4, and MnCl2

1979 ◽  
Vol 28 (1) ◽  
pp. 155-160 ◽  
Author(s):  
Jan J. Spitzer ◽  
Inger V. Olofsson ◽  
Prem Paul Singh ◽  
Loren G. Hepler
Keyword(s):  
Heat Capacities ◽  
Aqueous Electrolytes ◽  
Apparent Molar Heat Capacities
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