The Henderson Approximation and the Mass Action Law of Guldberg and Waage

TCE

The Chemical Educator

ISSN: 1430-4171 (electronic version)

Table of Contents

Abstract Volume 7 Issue 3 (2002) pp 132-135

The Henderson Approximation and the Mass Action Law of Guldberg and Waage

Robert de Levie

Department of Chemistry, Bowdoin College, Brunswick ME 04011
Received March 12, 2002. Accepted April 29, 2002

Published online: 17 May 2002

Abstract. Using contemporary accounts, we describe the scope of the Henderson approximation, and its relationship to the mass action law of Guldberg & Waage. The Henderson approximation, apparently written in logarithmic form by Hasselbalch, has the same form as the mass action law, but has a completely different meaning and a much more restricted range of applicability. The Guldberg-Waage law is the fundamental mass action relationship valid for all chemical equilibria, whereas the Henderson approximation is useful only within a limited range of a sufficiently concentrated two-component buffer mixture.

Key Words: In the Classroom; general chemistry; biochemistry, acid; equilibria

(*) Corresponding author. (E-mail: rdelevie@bowdoin.edu)

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