The Henderson-Hasselbalch Equation: Its History and Limitations

Abstract

Many students of chemistry have wondered if putting the mass action expression in logarithmic format should have warranted immortalization of the names Henderson and Hasselbalch. With focus on this question, this article examines the evolution of the Henderson-Hasselbalch equation and presents a critical evaluation of its usefulness. The discussion centers on the titration of a weak acid with sodium hydroxide. Approximate pH values obtained from the Henderson-Hasselbalch equation are compared with exact hydrogen ion concentrations and the percentage errors are displayed as a function of the acid dissociation constant and buffer composition (titration mixture).