ABSTRACT
This chapter discusses concepts and equations used to account for effects of ionic strength on equilibration reactions. The contribution of each ion to the ionic strength is one-half the product of the square of the charge on the ion times the concentration of the ion. The ionic strength of a solution is the sum of the contributions of all ions in the solution to the ionic strength. Ionic strengths calculated in this way are used to calculate activity coefficients of individual ions as well as mean activity coefficients for combinations of ions using the Debye-Hückel equation for ionic strengths up to about 0.10 M or the Davies equation for ionic strengths up to about 0.5 M. Procedures used to determine mean activity coefficients experimentally for selected situations are also discussed. However activity coefficients are obtained, they are used to convert equilibrium constants in terms of concentrations, called conditional constants, to constants in terms of activities, called thermodynamic constants. Finally, experimental results for the dissociation of acetic acid and the autoprotolysis of water are used to illustrate the use of extrapolation procedures to obtain thermodynamic constants from conditional constants.
