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Equilibrium in Chemistry

• Equilibrium refers to the state in a reversible reaction where the rates of the forward and reverse reactions are equal, leading to stable concentrations of reactants and products.

• Dynamic Nature: Although the concentrations of substances remain constant, both the forward and reverse reactions continue to occur, hence it's termed 'dynamic equilibrium'.

• Le Chatelier's Principle: This principle states that if an external change is applied to a system at equilibrium (such as concentration, temperature, or pressure), the system will adjust itself to counteract that change and restore a new equilibrium.

• Factors Affecting Equilibrium:

  1. Concentration Changes: Increasing the concentration of reactants shifts the equilibrium to the right (favoring products), while increasing product concentration shifts to the left (favoring reactants).

  2. Temperature Changes:

  • Exothermic reactions shift left when temperature is increased (favoring reactants).

  • Endothermic reactions shift right when temperature is increased (favoring products).

  3. Pressure Changes (for gaseous reactions): Increasing pressure shifts the equilibrium toward the side with fewer gas molecules.

• Equilibrium Constant (K): The equilibrium constant expression relates the concentrations of reactants and products at equilibrium. For the reaction:

  [ aA + bB \rightleftharpoons cC + dD ]

  The equilibrium constant K is given by:[ K = \frac{[C]^c [D]^d}{[A]^a [B]^b} ]where [ ] denotes the concentration of each species at equilibrium.

• Applications of Equilibrium: Knowledge of equilibrium is crucial in industrial processes, such as the Haber process for ammonia synthesis, where conditions are optimized for maximum yield.