This unit delves into the fundamental principles and concepts of acid-base equilibria. It begins by exploring various acid-base theories, including Arrhenius, Brønsted-Lowry, and Lewis concepts, providing a comprehensive framework for understanding acids and bases. The unit then examines the behavior of weak acids and bases in aqueous solutions, focusing on their ionization and the measures of their strengths. It also covers the common ion effect and the formation and function of buffer solutions, essential for maintaining pH stability in various chemical and biological systems. Finally, the unit addresses the hydrolysis of salts and the principles and applications of acid-base titrations, equipping students with the skills to perform and analyze titration experiments. Through this unit, students will gain a solid understanding of the chemical behavior of acids and bases, the factors affecting their equilibria, and the practical techniques used to measure and manipulate pH in different contexts.