Chemical equilibrum

Chemical Equilibrium Introduction Chemical equilibrium is a fundamental concept in chemistry that explains how reversible chemical reactions behave. Many chemical reactions do not go to completion; instead, they reach a state where reactants and products coexist. This condition is known as chemical equilibrium and is very important in understanding industrial processes, biological systems, and laboratory reactions. Meaning of Chemical Equilibrium Chemical equilibrium is the state of a reversible chemical reaction in which the rate of the forward reaction is equal to the rate of the backward (reverse) reaction, so that the concentrations of reactants and products remain constant with time. It is important to note that: Chemical equilibrium is dynamic, not static. Reactions continue to occur, but there is no net change in concentration. Reversible and Irreversible Reactions Reversible reactions are reactions that can proceed in both forward and backward directions. Represented using a double arrow (⇌) Example: Irreversible reactions proceed in one direction only. Represented using a single arrow (→) Example: Only reversible reactions can establish chemical equilibrium. Dynamic Nature of Chemical Equilibrium At equilibrium: The forward reaction continues converting reactants to products. The backward reaction continues converting products to reactants. The rates of both reactions are equal. Macroscopic properties such as colour, pressure, and concentration remain constant. Conditions Necessary for Chemical Equilibrium For chemical equilibrium to be established: The reaction must be reversible The reaction must occur in a closed system Suitable temperature and pressure conditions must be maintained Law of Chemical Equilibrium (Law of Mass Action) The law of mass action states that: At a constant temperature, the ratio of the product of the concentrations of the products to the product of the concentrations of the reactants, each raised to the power of their stoichiometric coefficients, is constant. This constant is known as the equilibrium constant (K). Equilibrium Constant (Kc and Kp) Kc (Concentration-based equilibrium constant) For a general reaction: The equilibrium constant expression is: Where: Square brackets [ ] represent molar concentration Solids and pure liquids are not included Kp (Pressure-based equilibrium constant) For gaseous reactions: