Reversible Reactions

• What is the focus of Specification Point 3.1.6.1?

  Chemical equilibria and Le Chatelier's principle
• What happens in reactions that proceed to completion?

  All reactants are fully converted into products
• What characterizes reversible reactions?

  Products can react to reform original reactants
• What is dynamic equilibrium in reversible reactions?

  Forward and reverse reactions occur at the same rate
• How is a reversible reaction denoted?

  With two opposing half-arrows: ⇌
• What occurs at dynamic equilibrium regarding concentrations?

  No net change in concentrations of reactants and products
• What is the equation representing dynamic equilibrium?


  A + B ⇌ C + D
• What is required for dynamic equilibrium to be achieved?

  A closed system where no substances can enter or leave
• How does Le Chatelier's Principle describe system responses?

  It describes adjustments to counteract changes
• Who formulated Le Chatelier's Principle and when?

  Henri Louis Le Chatelier in 1884
• What does Le Chatelier's Principle ensure for a system?

  The system returns to a stable state
• What happens if the concentration of reactants is increased in the Contact Process?

  The system shifts to the right, forming more SO₃
• What occurs if the concentration of products is increased in the Contact Process?

  The system shifts to the left, forming more SO₂ and O₂
• How does pressure affect equilibrium reactions involving gases?

  Increased pressure favors fewer gas molecules
• What happens to the equilibrium if pressure is increased in the Contact Process?

  The equilibrium shifts to the right, producing more SO₃
• What occurs if pressure is decreased in the Contact Process?

  The equilibrium shifts to the left, producing more SO₂ and O₂
• How does temperature affect equilibrium reactions?

  Increasing temperature shifts equilibrium left for exothermic reactions
• What happens if the temperature is increased in the Contact Process?

  The equilibrium shifts to the left, producing more SO₂ and O₂
• What occurs if the temperature is decreased in the Contact Process?

  The equilibrium shifts to the right, producing more SO₃
• What are compromise conditions in industrial processes?

  • Essential for balancing yield, rate, cost, and safety
  • Practical settings for efficient production
  • Used in the Haber process
• What is the Haber process and its reaction?

  • Synthesizes ammonia (NH₃) from nitrogen (N₂) and hydrogen (H₂)
  • Reaction: N₂ (g) + 3H₂ (g) ⇌ 2NH₃ (g)
  • ΔH = −92.4 kJ/mol
• What are the ideal and compromise conditions for temperature in the Haber process?

  • Ideal: Low temperature favors ammonia formation
  • Compromise: 450°C balances rate and yield
• What are the ideal and compromise conditions for pressure in the Haber process?

  • Ideal: High pressure favors ammonia formation
  • Compromise: 200 atmospheres maximizes yield safely
• What role does the catalyst play in the Haber process?

  • Iron catalyst with promoters increases reaction rate
  • Allows efficient operation at chosen temperature and pressure
• How has the Haber process been optimized in industry?

  It balances yield and rate effectively