Chemical Equilibrium Revision Sheet

1. 📌 Essentials

• Chemical equilibrium: State where concentrations of react and products remain constant over time in a reversible reaction.
• Reversible reactions: Reactions that proceed in both forward and reverse directions.
• Dynamic process: Reactions continue to occur, but net concentrations are unchanged.
• Equilibrium constant (Kc): Ratio of product concentrations to reactant concentrations at equilibrium, each raised to their stoichiometric powers.
• Expression for Kc: For $aA + bB \leftrightarrow cC + dD$,

  K_c = \frac{[C]^c [D]^d}{[A]^a [B]^b} 
  

• Magnitude of Kc:
  • $K_c \gg 1$: Equilibrium favors products.
  • $K_c \ll 1$: Equilibrium favors reactants.
  • $K_c \approx 1$: Both reactants and products are present in significant amounts.
• Le Châtelier’s Principle: System at equilibrium shifts to counteract any disturbance.
• Factors affecting equilibrium:
  • Changes in concentration
  • Temperature variations
  • Pressure (for gases)
  • Catalysts (speed up but do not shift equilibrium)

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