Chemical equilibrium: MCQ 4
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Questions and Answers

What is the direction of the equilibrium shift when the concentration of HI is increased?

  • Equilibrium remains unchanged
  • Equilibrium moves to the right
  • Equilibrium moves to the left (correct)
  • Equilibrium is unaffected
  • What is the effect of a decrease in temperature on the equilibrium of the reaction H₂ + I₂ → 2HI?

  • Equilibrium remains unchanged
  • Reaction rate increases
  • Equilibrium moves to the right (correct)
  • Equilibrium moves to the left
  • What is the effect of adding a catalyst to a reaction that has already reached equilibrium?

  • Equilibrium shifts to the right
  • Equilibrium shifts to the left
  • No effect on equilibrium (correct)
  • Reaction rate increases
  • What is the direction of the equilibrium shift when the pressure is increased in a gaseous reaction?

    <p>Equilibrium shifts to reduce the number of molecules</p> Signup and view all the answers

    What happens to the equilibrium of a reaction when the concentration of H₂ is decreased?

    <p>Equilibrium moves to the left</p> Signup and view all the answers

    What is the effect of a temperature increase on the equilibrium of the reaction H₂ + I₂ → 2HI?

    <p>Equilibrium moves to the left</p> Signup and view all the answers

    What is the direction of the equilibrium shift when the concentration of I₂ is decreased?

    <p>Equilibrium moves to the right</p> Signup and view all the answers

    What happens to the equilibrium when the pressure is increased?

    <p>Equilibrium moves to the right</p> Signup and view all the answers

    What is the optimal temperature used in the Haber process?

    <p>673K</p> Signup and view all the answers

    What is the purpose of a catalyst in the Haber process?

    <p>To lower the activation energy</p> Signup and view all the answers

    What happens to the equilibrium when the volume of the container is increased?

    <p>Equilibrium moves to the left</p> Signup and view all the answers

    What is the effect of adding HCL to the solution in the experiment to illustrate Le Chatelier's Principle?

    <p>The equilibrium shifts to the left</p> Signup and view all the answers

    What happens to the colour of the solution when it is heated?

    <p>The colour becomes less intense</p> Signup and view all the answers

    What is the effect of decreasing the pressure on the equilibrium?

    <p>Equilibrium moves to the left</p> Signup and view all the answers

    What is the purpose of the catalyst in the Haber process?

    <p>To lower the activation energy</p> Signup and view all the answers

    Study Notes

    Le Chatelier's Principle

    • Changes in concentration of one species:
      • Increasing [H₂] moves the equilibrium to the right
      • Increasing [HI] moves the equilibrium to the left
      • Decreasing [I₂] moves the equilibrium to the left

    Changes in Temperature

    • If temperature is lowered, the system tries to increase temperature
    • If temperature is raised, the system tries to lower temperature
      • Exothermic reaction releases heat, equilibrium moves to the right
      • Endothermic reaction absorbs heat, equilibrium moves to the left

    Addition of a Catalyst

    • A catalyst speeds up the reaction rate
    • Adding a catalyst at the start of a reaction helps reach equilibrium quicker
    • If added once equilibrium is reached, there is no effect on equilibrium

    Changes in Pressure

    • Increased pressure reduces the number of molecules in the container
    • Decreased pressure increases the number of molecules in the container
      • Example: If pressure increases, equilibrium moves to the right (4 molecules → 2 molecules)
      • If pressure decreases, equilibrium moves to the left
      • No effect if the number of molecules on either side of the equation is the same

    Changes in Volume of a Container

    • Increasing the volume means less pressure, equilibrium moves to the left
    • Decreasing the volume means more pressure, equilibrium moves to the right

    Industrial Applications

    • Manufacture of ammonia by the Haber process
    • Conditions: temperature (673K), pressure (200 atmospheres), catalyst

    Experiment to Illustrate Le Chatelier's Principle

    • Iron (III) chloride and potassium thiocyanate reaction
    • Subjecting the reaction to concentration changes and temperature changes
      • Concentration changes: adding HCL, potassium thiocyanate, or water
      • Temperature changes: hot water or ice water
      • Effects on the equilibrium reaction

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    Description

    Understanding Le Chatelier's Principle in chemistry, including how changes in concentration and temperature affect equilibrium. Learn how the system responds to changes in reactants and temperature.

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