Journal of Solution Chemistry

, Volume 8, Issue 5, pp 329–345

Ionization of aqueous benzoic acid: Conductance and thermodynamics

  • Laurence E. Strong
  • Thomas Kinney
  • Paul Fischer

DOI: 10.1007/BF00646786

Cite this article as:
Strong, L.E., Kinney, T. & Fischer, P. J Solution Chem (1979) 8: 329. doi:10.1007/BF00646786


Molar conductances of dilute aqueous benzoic acid solutions are presented for temperatures from 5 to 80°C. The data have been analyzed to give acid dissociation constants as well as ΔHo, ΔSo, and ΔCpo for the ionization process and the limiting conductance of the benzoate ion. The conductance-viscosity product changes less than 4% over the temperature range, indicating that the interaction of the benzoate ion with the solvent changes little if at all with increasing temperature. The pKa(m) vs.T data show that ΔHo decreases quadratically while ΔCpo increases linearly withT although, over the 75°C range, ΔCpo increases only about 6 cal-mole−1 deg−1 around an average of −37 cal-mole−1deg−1. The acid dissociation constants as derived from the conductance-molal concentration analysis show an average uncertainty of about 0.1% and are fitted to within about 0.01% by the equation
$$p{\text{K}}_{\text{a}} (m) = - 75.5422 + 3136.34/T + 28.7965 log T - 6.8139 {\text{x}} 10^{ - 3{\text{T}}} $$
whereT is the absolute temperature.

Key words

Benzoic acid ionization constant molar conductance enthalpy entropy heat capacity benzoate ion conductance Walden product 

Copyright information

© Plenum Publishing Corporation 1979

Authors and Affiliations

  • Laurence E. Strong
    • 1
  • Thomas Kinney
    • 2
  • Paul Fischer
    • 3
  1. 1.Department of ChemistryEarlham CollegeRichmond
  2. 2.The Medical College of PennsylvaniaPhiladelphia
  3. 3.University of Connecticut School of MedicineFarmington

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