2.2 Activity Scales, pH and Activity Coefficients

OVERVIEW

The goals of this module are to understand the different activity scales used to express pH and ionization constants (pK_A’s and pK_B's), and to learn a few simple equations for calculating activity coefficients.

KEY CONCEPTS

1. The differences among the infinite dilution and ionic medium activity scales for ionization constants.
2. The differences among the infinite dilution, ionic medium and NIST scales for pH.
3. The mathematical formula for calculation of ionic strength.
4. The most common expressions for calculating activity coefficients and their ranges of validity.