Titrimetric Study of the Solubility and Dissociation of Benzoic Acid in Water: Effect of Ionic Strength and Temperature


The apparent acid dissociation constant (Kc) of benzoic acid in water has been determined ti-trimetrically under ionic strength values between 0.00 and 0.50 mol·L﹣1 at a range of temperatures between 16°C and 41°C. The thermodynamic dissociation constant (as pKa) of benzoic acid was determined as 4.176 at 25°C. No regular correlation between pKa of benzoic acid and the temperature in the range was used. The values of pKa are inversely proportional to temperatures between 16°C and 30°C. In this range of temperature, the values of thermodynamic quantities () for the dissociation process of benzoic acid in water were calculated by using Van’t Hoff plot. For this case the dissociation was not favoured through entropy and enthalpy changes. The values of pKa are directly proportional to temperatures between 30°C and 41°C.

Share and Cite:

Khouri, S. (2015) Titrimetric Study of the Solubility and Dissociation of Benzoic Acid in Water: Effect of Ionic Strength and Temperature. American Journal of Analytical Chemistry, 6, 429-436. doi: 10.4236/ajac.2015.65042.

Conflicts of Interest

The authors declare no conflicts of interest.


[1] Smetana, A.J. and Popov, A.I. (1979) On the Influence of Ionic Strength on Equilibrium Constant of Ion-Molecule Reaction. Journal of Chemical Thermodynamics, 11, 1145-1149.
[2] Tawarah, K.M. and Khouri, S.J. (2000) Determination of the Stability and Stoichiometry of p-Methyl Red Inclusion Complexes with γ-Cyclodextrin. Dyes and Pigments, 45, 229-233.
[3] Sergeeva, V.F. (1965) Salting-Out and Salting-In of Non-Electrolytes. Russian Chemical Reviews, 34, 309-318.
[4] Albert, A. and Serjeant, E.P. (1984) The Determination of Ionization Constants. 3rd Eddition, Chapman and Hall, London.
[5] Atkins, P. and de Paula, J. (2010) Physical Chemistry. 9th Eddition, W.H. Freeman and Company, New York.
[6] Vogel, A. (1989) Text-Book of Quantitative Chemical Analysis. 5th Edition, Longman, Harlow.
[7] Sarmini, K. and Kenndler, E. (1998) Capillary Zone Electrophoresis in Mixed Aqueous-Organic Media: Effect of Organic Solvents on Actual Ionic Mobilities, Acidity Constants and Separation Selectivity of Substituted Aromatic Acids II. Ethanol. Journal of Chromatography A, 811, 201-209.
[8] Christensen, J.J., Hensen, L.D. and Izaft, R.M. (1976) Handbook of Ionization Constants. Wiley Interscience, New York.
[9] Bosch, E., Bou, P., Allemann, H. and Rosés, M. (1996) Retention of Ionizable Compounds on HPLC. pH Scale in Methanol-Water and the pK and pH Values of Buffers. Analytical Chemistry, 68, 3651-3657.
[10] Cleveland, J.A., Benko Jr, M.H., Gluck, S.J. and Walbroehl, Y.M. (1993) Automated pKa Determination at Low Solute Concentrations by Capillary Electrophoresis. Journal of Chromatography A, 652, 301-308.
[11] Solomons, G.T. and Fryhle, C.B. (2011) Organic Chemistry. 10th Edition, John Wiley & Sons, Inc., Hoboken.

Copyright © 2022 by authors and Scientific Research Publishing Inc.

Creative Commons License

This work and the related PDF file are licensed under a Creative Commons Attribution 4.0 International License.