This lecture covers the calculation of pH for strong and weak acids, strong and weak bases, and salts in water. It explains how dilution affects equilibrium, the shift in balance towards products, and the application of the Le Chatelier principle. Examples of strong and weak acids are provided, along with the pH calculations for each. The lecture also discusses the pH of buffer solutions, the role of species in acid-base reactions, and the influence of salts on solution pH. It concludes with the impact of certain salts on solution pH and the identification of acidity/basicity of dissolved ions.