Thermodynamic properties of the ionization of morpholine as a function of temperature and ionic strength

Moira K. Ridley, Caibin Xiao, Donald A. Palmer, David J. Wesolowski

Research output: Contribution to journalArticlepeer-review

14 Scopus citations

Abstract

A hydrogen-electrode concentration cell was used to monitor pH in a study of morpholine ionization in aqueous solutions to temperatures of 290°C and to ionic strengths of 1 m, maintained with either sodium trifluoromethanesulfonate or sodium chloride. The resulting hydrolysis quotients were combined with values from two previous potentiometric investigations of this reaction, as well as existing heat capacity and apparent molar volume data, to provide a global fitting equation. The computed thermodynamic parameters for the acid dissociation of the morpholinium ion at 25°C and infinite dilution are log K = (-8.491 ± 0.003); ΔH = (39 ± 1) kJ·mol-1; ΔS = (-31 ± 1) J·K-1·mol-1; ΔCp = (40 ± 7) J·K-1·mol-1; and ΔV = (3 ± 1) cm3·mol-1. At low ionic strengths, including values at infinite dilution, the log Q data were found to be near linear with respect to the reciprocal temperature in Kelvin over the measured temperature range of 0°C to 300°C.

Original languageEnglish
Pages (from-to)502-507
Number of pages6
JournalJournal of Chemical and Engineering Data
Volume45
Issue number3
DOIs
StatePublished - May 2000

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