The “extent of reaction”: a powerful concept to study chemical transformations at the first-year general chemistry courses

The concept of extent of reaction was discussed many times in physical chemistry journals and books. This contribution strongly suggests the use of the extent of reaction as standard basic tool in teaching stoichiometry. The same idea was suggested several times in the past without success because the concept of extent of reaction is still not presented in the first-year general chemistry textbooks. It is also remarked that the concept of extent of reaction represents a simple example of the way of attaining a mathematization of chemistry, that is chemistry thought and made with the mathematical way of thinking, i.e. using variables, symbols and functions. Presenting the concept of the extent of reaction within the general chemistry curriculum will support successive physical chemistry courses, as these courses make extensive use of this powerful concept when teaching thermodynamics and kinetics of chemical reactions.