A definição ácido-base de Arrhenius dos livros-textos de química: a história de um obstáculo epistemológico e suas consequências para o ensino-aprendizagem

Abstract

The so-called Arrhenius acid-base definition, present in several Chemistry textbooks in Brazil, was considered both from an epistemological point of view and from a historical point of view. No bibliographic evidence was found to demonstrate that Arrhenius coined any acid-base definition, and from this finding it is proposed that the definition attributed to Arrhenius in textbooks is an accommodation/amalgamation of Arrhenius' electrolytic dissociation theory with the long-lived Liebig definition of acids, based on the presence of hydrogen and widely accepted by chemists in the 19th century. The acid-base definition attributed to Arrhenius in textbooks is also erroneous, since acidic or basic aqueous solutions can be prepared without adding solutes containing hydrogen or hydroxyl ions. It is argued that the substantialist epistemological obstacle represented by hydrogen was responsible for the transfer of allegiance of the Liebig definition of acids to the Arrhenius ionic theory, since this can explain the reactivity of acids and electrolytes in general in aqueous solution. The consequences of teaching the erroneous acid-base definition attributed to Arrhenius in textbooks are discussed in terms of epistemological obstacles, and didactic strategies for dealing with these obstacles are presented and discussed.