ISSN:
1572-8927
Keywords:
Oxalic acid
;
ethanedioic acid
;
dissociation constants
;
thermodynamics
;
potentiometry
;
ionic strength
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
Notes:
Abstract The first and second molal dissociation quotients of oxalic acid were measured potentiometrically in a concentration cell fitted with hydrogen electrodes. The emf of oxalic acid-bioxalate solutions was measured relative to an HCl standard solution from 25 to 125°C over 25o intervals at nine ionic strengths ranging from 0.1 to 5.0 molal (NaCl). The molal dissociation quotients and available literature data were treated in the all anionic form by a five-term equation that yielded the following thermodynamic quantities at infinite dilution and 25°C: logK1a=−1.277±0.010, ΔH 1a o =−4.1±1.1 kJ-mol−1, ΔS 1a o =38±4 J-K−1-mol−1, and ΔC p,1a o =−168±41 J-K−1-mol−1. Similar measurements of the bioxalate-oxalate system were made at 25o intervals from 0 to 175°C at seven ionic strengths from 0.1 to 5.0m. A similar regression of the experimentally-derived and published equilibrium quotients using a seven-term equation yielded the following values at infinite dilution and 25°C: logK2a=−4.275±0.006, ΔH 2a o =−6.8±0.5 kJ-mol−1, ΔS 2a o =−105±2 J-K−1-mol−1, and ΔC p,2a o =−261±12 J-K−1-mol−1.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01074952
