The equilibrium constant for bromothymol blue: A general chemistry laboratory experiment using spectroscopy

Abstract

A simple, inexpensive, and environmentally friendly undergraduate laboratory experiment is described in which students use visible spectroscopy to determine a numerical value for an equilibrium constant, Kc. The experiment correlates well with the lecture topic of equilibrium even though the subject of the study is an acid-base indicator, bromothymol blue. The experiment gives excellent results and offers an inexpensive, zero-waste alternative to traditional equilibrium experiments, such as the Fe(SCN) 2+ equilibrium. © 2011 The American Chemical Society and Division of Chemical Education, Inc.