Chapter 10: Reaction Rates and Equilibrium

• What type of system is required for reversible reactions to reach dynamic equilibrium?

  A closed system
• What is the definition of dynamic equilibrium in a reversible reaction?

  Reactants form as fast as products
• In dynamic equilibrium, what remains constant?

  Concentrations of each substance
• At equilibrium, are the forward and reverse reactions still occurring?

  Yes, they are both still happening
• At equilibrium, how do the rates of the forward and reverse reactions compare?

  They are the same
• At equilibrium, what happens to the concentration of reactants and products?

  It remains constant
• What principle describes how a system at equilibrium responds to a change?

  Le Chatelier’s principle
• According to Le Chatelier's principle, what changes can affect the position of equilibrium?

  Concentration, pressure, or temperature
• According to Le Chatelier's principle, if the concentration of a reactant is increased, how does the equilibrium shift?

  To favour product formation
• If more product is added to a reaction at equilibrium, how will the equilibrium shift?

  To favor reactant formation
• According to Le Chatelier's principle, if the pressure is increased, how does the equilibrium shift?

  To the side with fewest gas moles
• In the synthesis of ammonia, which side does the equilibrium shift towards when pressure is increased?

  Towards ammonia
• If pressure is decreased, which side will the equilibrium shift towards?

  The side with more moles
• According to Le Chatelier's principle, if the temperature is increased, how does the equilibrium shift?

  In the endothermic direction
• If the forward reaction is endothermic, how will increasing temperature affect the equilibrium?

  Shift towards the products
• If the reverse reaction is exothermic, how will decreasing the temperature affect the equilibrium?

  Shift towards the reactants
• How does a catalyst affect the position of equilibrium?

  It does not change it
• Why doesn't a catalyst change the position of equilibrium?

  Speeds forward and reverse equally
• In industrial processes involving reversible reactions, what do manufacturers consider to maximize yield?

  Temperature, pressure, concentration
• What else besides yield do manufacturers need to consider for industrial processes?

  Reaction rate, cost, safety
• For exothermic reactions, why might moderate temperatures be used instead of low temperatures?

  Satisfactory yield at reasonable rate
• Why might moderate conditions be used for industrial processes?

  • Low pressures result in a slow rate of reaction.
  • High pressures are expensive to generate, require specialist equipment and may result in unwanted side reactions.
  • Low temperatures result in a slow rate of reaction.
  • High temperatures are expensive and involve burning lots of fuel, which releases carbon dioxide and therefore not very environmentally-friendly).
• What is the equilibrium constant denoted by?

  Kc
• What does a larger value of Kc indicate?

  Equilibrium lies to the right
• What does a smaller value of Kc indicate?

  Equilibrium lies to the left
• For which type of reaction can we calculate Kc?

  Homogenous reaction
• In which state must the reactants and products be to calculate Kc?

  Same state