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Direction of Reversible Reactions

The direction of a reversible reaction depends on reactant and product concentrations and the reaction quotient (Q) compared to the equilibrium constant (K).

Key Concepts​

  • Reversible Reaction: Can proceed in both forward and reverse directions
  • Reaction Quotient (Q): Q = [products]^coeff / [reactants]^coeff at any point in time
  • Compare Q to K:
    • Q < K → reaction proceeds forward (toward products)
    • Q = K → reaction is at equilibrium
    • Q > K → reaction proceeds reverse (toward reactants)

Example​

For N₂ + 3 H₂ ⇌ 2 NH₃:

  • If initial concentrations give Q = 0.5 and K = 1.0 → reaction moves forward
  • If Q = 2.0 and K = 1.0 → reaction shifts backward

Importance​

  • Predicts which way a reaction will shift when conditions change
  • Helps in controlling reaction yield in industrial and laboratory settings
  • Essential for understanding chemical equilibrium and Le Chatelier's Principle

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