Making Assumptions Explicit: How the Law of Conservation of Matter Can Explain Empirical Formula Problems

Abstract

The law of conservation of matter plays an important part in the story of the determination of the empirical formula of a compound. Utilizing the law of conservation could promote student understanding of this subject by providing the rationale for many of the procedural steps used to solve empirical formula problems. This is an argument for linking theory to method. It is not pedagogically sound for students to simply go through a series of steps and arrive at an answer without knowing why these steps can be performed, what assumptions they rest on, and how they relate to other chemical concepts. With this in mind, a table was constructed that explicitly connects theoretical assumptions of conservation to the procedural steps followed by introductory students when determining the empirical formula of an unknown compound.