Apparent and partial molar heat capacities and volumes of chromates (CrO42-(aq), HCrO4-(aq), and Cr2O72-(aq)) at 25.degree.C: chemical relaxation and calculation of equilibrium constants for high temperatures

1990 ◽  
Vol 94 (20) ◽  
pp. 7821-7830 ◽  
Author(s):  
Jamey K. Hovey ◽  
Loren G. Hepler
Keyword(s):  
High Temperatures ◽  
Equilibrium Constants ◽  
Heat Capacities ◽  
Partial Molar Heat Capacities ◽  
Chemical Relaxation

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.

Thermodynamic properties of aqueous diethanolamine (DEA), N,N-dimethylethanolamine (DMEA), and their chloride salts: apparent molar heat capacities and volumes at temperatures from 283.15 to 328.15 K

2000 ◽  
Vol 78 (1) ◽  
pp. 151-165 ◽  
Author(s):  
Christopher Collins ◽  
Joelle Tobin ◽  
Dmitri Shvedov ◽  
Rom Palepu ◽  
Peter R Tremaine
Keyword(s):  
Partial Molar Volumes ◽  
Heat Capacities ◽  
Apparent Molar Heat Capacities ◽  
Molar Volumes ◽  
Partial Molar Heat Capacities ◽  
Relaxation Effects ◽  
Chemical Relaxation ◽  
Young's Rule ◽  
Vibrating Tube Densimeter ◽  
Chloride Salts

Apparent molar heat capacities Cp,ϕ and apparent molar volumes Vϕ for aqueous diethanolamine (HOC2H4)2NH, diethanolammonium chloride (HOC2H4)2NH2Cl, N,N'-dimethylethanolamine (HOC2H4)(CH3)2N, and N,N'-dimethylethanolammonium chloride (HOC2H4)(CH3)2NHCl were determined from 283.15 to 328.15 K with a Picker flow microcalorimeter and vibrating tube densimeter. The experimental results have been analyzed in terms of Young's Rule with the Guggenheim form of the extended Debye-Hückel equation and appropriate corrections for chemical relaxation effects. These calculations lead to standard partial molar heat capacities and volumes for the neutral amines, (HOC2H4)2NH(aq) and (HOC2H4)(CH3)2N(aq), and the ions (HOC2H4)2NH2+(aq) and (HOC2H4)(CH3)2NH+(aq) over the experimental temperature range. Key words: standard partial molar volumes, standard partial molar heat capacities, diethanolamine, dimethyethanolamine, aqueous alkanolamine ionization.

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.

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