Abstract

We present a critical discussion of how chemistry textbooks treat the electrolysis of water and aqueous salt solutions. Our analysis is based on a survey of general chemistry textbooks in English and Korean at secondary and tertiary levels, also informed by our own experiments and the historical background of 19th-century debates. English- language textbooks present various and contradictory accounts of the electrolysis of water; a key point of disagreement is whether hydrogen and oxygen gases originate from pre-existing H+ and OH- ions, or from the direct reduction and oxidation of H2O molecules. School textbooks in Korea all present the same account, with no indication of alternative views. A vast majority of all texts ignore the possibility that H2 and O2 may result from secondary reactions, which was a standard view in the late 19th century following the works of Daniell and Miller. Concerning the electrolysis of aqueous salt solutions, all of the treatments we have found give oversimplified views of competing reactions based on standard reduction/oxidation potentials. It is understandable that textbooks try to present sufficiently simple pictures that students at each level can handle; however, this should not be done in a way that shuts down questions. We believe that a judicious admission of complexity would be beneficial in encouraging students toward further learning and investigation.

Hasok Chang is the Hans Rausing Professor of History and Philosophy of Science at the University of Cambridge, and holds one of the very prestigious British Academy/Wolfson Research Professorships. Katy Duncan is a PhD candidate in the Department of History and Philosophy of Science