Geometrical description of chemical equilibrium and Le Châtelier’s principle: Two-component systems

Chemical equilibrium is one of the most important concepts in chemistry. The changes in properties of the chemical system at equilibrium induced by variations in pressure, volume, temperature, and concentration are always included in classroom teaching and discussions. This work introduces a novel, geometrical approach to understanding the chemical system at equilibrium with the example of a simple two-component system and shows how the equilibrium changes under the influence of external perturbations. The paper discusses how thermodynamic factors (contained in the equilibrium constant K) and the conservation of mass principle govern the equilibrium state. The equilibrium and its changes are described using the geometrical representation in concentration space. The goal of this work is to help students better understand the basis behind the well-known Le Châtelier’s principle and equilibrium in general.