Chemical Equilibrium

Introduction

• The ionization of weak acids and weak bases are reversible reactions.
• Reversible reactions include both forward and backward reactions.

Chemical Reactions

• There are two types of chemical reactions:
  • Reversible Reaction:
    • The reactant changes into product and the product changes back to reactant.
    • The concentration of the reactant is never zero.
    • Example: Ionization of weak acids and weak bases.
  • Irreversible Reaction:
    • Proceed in only one direction.
    • The reactant completely transforms into the product at a certain time.

State of Equilibrium

• Equilibrium is the state where the measurable properties of the reaction do not change over time.
• Equilibrium is established when the rate of forward and backward reactions is equal.

Physical and Chemical Equilibrium

• Physical Equilibrium:
  • Example: Transition from solid to liquid (melting) and from liquid to solid (freezing).
• Chemical Equilibrium:
  • Example: A + B → Product (Chemical change).

Equilibrium Constant

• There are two types of equilibrium constants:
  • Kc (in terms of concentration)
  • Kp (in terms of partial pressure)
• The state of the equilibrium constant depends on temperature.

Factors Affecting Equilibrium

• Factors affecting equilibrium:
  • Concentration
  • Temperature
  • Pressure

Effect of Concentration

• Increasing the concentration of a reactant or product will shift the equilibrium in the direction that reduces the effect of the added substance.

Effect of Temperature

• Endothermic Reaction: Increasing temperature raises the equilibrium constant.
• Exothermic Reaction: Increasing temperature lowers the equilibrium constant.

Effect of Pressure

• If pressure is increased, the equilibrium will shift in the direction with fewer gaseous molecules.

Simultaneous Equilibrium

• When more than one equilibrium exists in a mixture, the concentration of common substances is the same in all equilibria.

Conclusion

• Understanding chemical equilibrium and its principles is important for knowing the direction of reactions and equilibrium constants.

• Thank you for attending this session. See you in the next session.