Lecture.1: CHEMISTRY PART-1, ||CHAPTER NO:8|| INTRODUCTION TO CHEMICAL EQUILIBRIUM

Chapter 8: Introduction to Chemical Equilibrium Chemical equilibrium is a fundamental concept in chemistry that explains how chemical reactions behave when they do not go to completion. Many reactions are reversible in nature, meaning they can proceed in both the forward and reverse directions. Chemical equilibrium describes the state in which these opposing reactions occur at equal rates, resulting in constant concentrations of reactants and products. Types of Chemical Reactions Based on the direction in which reactions proceed, chemical reactions are mainly classified into two types: Irreversible Reactions These reactions proceed only in one direction and continue until one or more reactants are completely consumed. Such reactions are represented by a single arrow (→). Example: Combustion of carbon: C + O₂ → CO₂ Reversible Reactions These reactions proceed in both forward and backward directions simultaneously. They are represented by a double arrow (⇌). Example: Formation of ammonia (Haber process): N₂ + 3H₂ ⇌ 2NH₃ Most reactions that occur in closed systems and involve gases or solutions are reversible and can attain equilibrium. Chemical Equilibrium Chemical equilibrium is defined as the dynamic state of a reversible reaction in which the rate of the forward reaction equals the rate of the reverse reaction. At this stage, there is no net change in the concentrations of reactants and products, even though reactions continue to occur at the molecular level. Key features of chemical equilibrium include: It is dynamic, not static. It is achieved only in reversible reactions. It occurs in a closed system. Concentrations of reactants and products remain constant, not necessarily equal. At equilibrium, macroscopic properties such as pressure, color, and concentration remain unchanged, indicating balance within the chemical system. Importance of Chemical Equilibrium Understanding chemical equilibrium is essential for controlling industrial processes, predicting reaction behavior, and optimizing product yield in chemical manufacturing. It also forms the basis for studying equilibrium constants, Le Chatelier’s principle, acids and bases, and solubility equilibria. In summary, chemical equilibrium provides a clear explanation of how reversible reactions stabilize over time, highlighting the balance between opposing chemical processes and forming a cornerstone of physical chemistry.