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Cyanide Thermodynamics. III. Enthalpies and Entropies of Ionization of Water and Hydrogen Cyanide

Solis, J.S., May, P.M. and Hefter, G. (1996) Cyanide Thermodynamics. III. Enthalpies and Entropies of Ionization of Water and Hydrogen Cyanide. Australian Journal of Chemistry, 49 (6). pp. 651-657.

Link to Published Version: http://dx.doi.org/10.1071/CH9960651
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Abstract

The heats (enthalpy changes) associated with the ionization of water and of hydrogen cyanide have been determined by titration calorimetry at 25°C as a function of ionic strength up to 5 M in both NaCl and NaClO4 media. The enthalpy changes for both reactions exhibit a 'medium effect' with ΔH being more positive in NaCl than in NaClO4 and with the difference becoming more pronounced with increasing ionic strength. This is attributed to the greater solvation of Cl- cf. CN- in aqueous solution. The present ΔH values are similar to previous published results at high ionic strengths, and are in excellent agreement with the well established literature values at infinite dilution. The present ΔH values were combined with literature stability constant data to calculate the corresponding entropies for the ionization of H2O and HCN as a function of ionic strength.

Publication Type: Journal Article
Murdoch Affiliation: School of Chemical and Mathematical Science
Publisher: Commonwealth Scientific and Industrial Research Organization Publishing
URI: http://researchrepository.murdoch.edu.au/id/eprint/1270
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