Equilibria

• What is the focus of AQA A Level Chemistry in this document?

  Chemical Equilibria, Le Chatelier’s Principle & Kc
• What is a reversible reaction?

  • Products can reform original reactants
  • Opposite reactions occur simultaneously
  • Represented by two opposing half arrows: ⇌
• What does dynamic equilibrium mean?

  Reactants and products are constantly moving
• What happens at dynamic equilibrium in a closed system?

  Rates of forward and backward reactions are equal
• What does a closed system mean in chemical reactions?

  No reactants or products escape the mixture
• How does an open system differ from a closed system?

  Open systems allow matter and energy loss
• When can equilibrium be reached in open flasks?

  When negligible material is lost through evaporation
• What is the effect of losing gas in an open system?

  Reaction goes to completion
• What is Le Chatelier's Principle?

  • If a change is made to a system in equilibrium,
  • The position of equilibrium shifts to counteract the change
  • Predicts effects of temperature, pressure, or concentration changes
• What does it mean when the position of equilibrium shifts to the left?

  Concentration of reactants increases
• What does it mean when the position of equilibrium shifts to the right?

  Concentration of products increases
• What happens to equilibrium when more ethyl ethanoate is added?

  Equilibrium shifts to the left
• What happens to equilibrium when some ethanol is removed?

  Equilibrium shifts to the left
• What is the effect of adding water to an equilibrium mixture?

  No effect on equilibrium position
• How does pressure affect equilibrium in gas reactions?

  Only affects reactions with gases
• What happens to equilibrium when pressure is increased in a gas reaction?

  Shifts towards fewer gas molecules
• What is the effect of temperature on equilibrium constant K?

  Changes in temperature affect K's value
• What happens to equilibrium when temperature is increased in an endothermic reaction?

  Equilibrium shifts to the right
• What happens to equilibrium when temperature is increased in an exothermic reaction?

  Equilibrium shifts to the left
• What is the role of a catalyst in a chemical reaction?

  Increases rate of both forward and reverse reactions
• How does a catalyst affect the position of equilibrium?

  No effect on the position of equilibrium
• What factors affect the equilibrium constant K?

  • Changes in temperature affect K
  • Changes in concentration do not affect K
  • Changes in pressure do not affect K
• What is the effect of increasing pressure on the Haber process?

  Shifts equilibrium towards fewer gas molecules
• What is the compromise pressure used in the Haber process?

  200 atm
• What is the compromise temperature used in the Haber process?

  400−450 °C
• What happens when ammonia is removed from the reaction mixture?

  Equilibrium shifts to the right
• What is the role of vanadium(V) oxide in the Contact process?

  Acts as a catalyst to increase reaction rate
• What happens to the equilibrium constant K when a catalyst is added?

  K remains unchanged
• Why is understanding equilibrium important in the chemical industry?

  • Equilibrium reactions are crucial in large-scale production
  • Helps in maximizing yields of chemicals
  • Essential for efficient chemical processes
• What is the reaction for the synthesis of ammonia in the Haber process?

  3H₂(g) + N₂(g) ⇌ 2NH₃(g)
• What is the effect of increasing temperature on the equilibrium constant K for an endothermic reaction?

  K increases
• What is the effect of increasing temperature on the equilibrium constant K for an exothermic reaction?

  K decreases
• What is the reaction for the synthesis of sulfuric acid in the Contact process?

  2SO₂(g) + O₂(g) ⇌ 2SO₃(g)
• What happens to the equilibrium constant K when the concentration of reactants changes?

  K remains unchanged
• What happens to the equilibrium constant K when the pressure changes?

  K remains unchanged
• What happens to the equilibrium constant K when the temperature changes?

  K is affected by temperature changes
• What is the effect of a catalyst on the rate of reaction?

  Increases the rate of both forward and reverse reactions
• What is the effect of a catalyst on the position of equilibrium?

  No effect on the position of equilibrium
• What is the importance of maximizing yield in chemical reactions?

  Increases efficiency and profitability of processes
• What is the significance of the Haber process in industry?

  Produces ammonia for fertilizers