Abstract

The electrolysis of water and aqueous salt solutions is a common and significant subject in chemistry instruction at various levels.

However, textbook treatments of electrolysis are often inadequate and misleading, and also mutually contradictory. In this paper we present an analysis of a number of chemistry textbooks at GCSE , A-level, and introductory university levels, supplemented by our own experimental work and some relevant historical perspective.

In the electrolysis of water there are open questions about whether the resultant hydrogen and oxygen gases originate from pre-dissociated ions, or a direct reduction and oxidation of H2O molecules. Hardly any textbooks give a convincing account of the precise role played by the added electrolyte to facilitate the electrolysis of water. And generally there is an unnecessary downplaying of the various interesting secondary reactions in electrolysis. We argue that the textbook treatments would be improved by an admission of complexities that can spur students on to further learning, and a recognition that there are viable competing accounts. In fact, we argue that the most insightful elementary model of electrolysis was advanced in the mid-19th century by J F Daniell and W A Miller, an account that is almost universally ignored in modern textbooks.

We conclude with a brief discussion of broader implications of this study for science education in general.