The enthalpy of formation of magnesium sulfate ion pairs

Wing H. Leung, Frank J. Millero

Research output: Contribution to journalArticle

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Abstract

The enthalpies of dilution of lithium, sodium, potassium, and magnesium chloride and sulfate solutions in the range 0.1 to 1.0 m have been measured at 30°C with a microcalorimeter. The relative apparent enthalpies φL of these solutions have been determined with the aid of an extended form of the Debye-Hückel limiting law {Mathematical expression} where SH is the limiting-law slope, σ = 3/I3/2 × [(1+I1/2 - 1/(1+I1/2 - 2 ln (2+I1/2)], and B and C are empirical constants. This equation fits the experimental results to within a standard deviation of 2 cal-mole-1 for all the salts. The measured φL for the MgSO4 solutions were compared to those calculated using the additivity principle, φL(MgCl2) + φL(Na2SO4) - 2φL(NaCl), and the extended Debye-Hückel equation. The results of this comparison have been used to calculate the ΔHAo for the formation of MgSO40. A value of ΔHAo = 1.15 to 1.36 was obtained, depending upon the φL estimates for the free ions Mg2+ and SO42-. The results are briefly discussed and compared to the results obtained by other workers.

Original languageEnglish (US)
Pages (from-to)145-159
Number of pages15
JournalJournal of Solution Chemistry
Volume4
Issue number2
DOIs
StatePublished - Feb 1 1975

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Keywords

  • Enthalpy
  • dilution
  • ion pairs
  • lithium, sodium, and potassium chlorides and sulfates

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Molecular Biology
  • Physical and Theoretical Chemistry

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