This lecture covers the concept of chemical equilibrium, defining the reaction quotient and equilibrium constant for reactions in both homogeneous and heterogeneous systems. It explains how to predict the direction of a reaction based on Q and K values, and how disturbances can shift the equilibrium. The lecture also discusses the effect of temperature changes on equilibrium constants, the impact of adding or removing substances on equilibrium, and the role of pressure and volume changes. Additionally, it explores the solubility product and its relation to equilibrium constants, as well as practical applications in industrial chemistry.