Lesson 3.2.3

3.2.3 Chemical equilibrium Quiz: OCR Chemistry, Unit 2

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 3.2.3, Chemical equilibrium: 20 multiple choice questions for the OCR Chemistry (H432), Unit 2: Periodic table and energy, written with Revision Ninja.

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The 20 questions

  1. What feature is equal for both forward and reverse reactions at dynamic equilibrium?

    • Reaction rates
    • Mole fractions
    • Activation energies
    • Reactant concentrations

  2. Which direction does the position of equilibrium shift when temperature is increased for an exothermic reaction?

    • To the left
    • No shift
    • Symmetrically
    • To the right

  3. Increasing total pressure shifts a gaseous equilibrium towards which side?

    • Fewer gas moles
    • More gas moles
    • Reactants only
    • Same gas moles

  4. How does adding a catalyst affect the position of a dynamic equilibrium?

    • No effect
    • Shifts left
    • Shifts right
    • Increases yield

  5. Why is a compromise temperature used industrially for exothermic equilibrium reactions?

    • Purity versus toxicity
    • Rate versus yield
    • Pressure versus volume
    • Cost versus safety

  6. What is the Kc expression for N2 + 3H2 ⇌ 2NH3?

    • [N2][H2]^3 / [NH3]^2
    • [NH3]^2 / ([N2] + [H2]^3)
    • [NH3] / ([N2][H2])
    • [NH3]^2 / ([N2][H2]^3)

  7. At equilibrium for A + 2B ⇌ C, [A] = 0.20, [B] = 0.50 and [C] = 0.10 mol dm-3. What is the value of Kc?

    • 2.0
    • 10.0
    • 5.0
    • 0.4

  8. What does a very large value of the equilibrium constant Kc indicate?

    • Mostly products
    • Equal amounts
    • No reaction
    • Mostly reactants

  9. What does a very small value of the equilibrium constant Kc indicate?

    • Equal amounts
    • Fast reaction
    • Mostly reactants
    • Mostly products

  10. Which way does the equilibrium position shift if additional reactant is added?

    • Upwards
    • No change
    • To the right
    • To the left

  11. Which way does the equilibrium position shift if a product is continuously removed?

    • Inwards
    • No change
    • To the left
    • To the right

  12. How does increasing the temperature affect the value of Kc for an endothermic reaction?

    • Kc becomes zero
    • Kc stays constant
    • Kc increases
    • Kc decreases

  13. What effect does changing pressure have on an equilibrium with equal gas moles on both sides?

    • No effect
    • Increases yield
    • Shifts left
    • Shifts right

  14. In H2 + I2 ⇌ 2HI, the equilibrium concentrations are [H2] = [I2] = 0.10 and [HI] = 0.80 mol dm-3. What is Kc?

    • 8.0
    • 0.125
    • 64
    • 16

  15. Why does adding a catalyst shorten the time taken to reach dynamic equilibrium?

    • Increases forward rate
    • Increases equilibrium yield
    • Lowers product energy
    • Increases both rates

  16. What is the main industrial drawback of using extremely high pressure in equilibrium reactions?

    • Reduced product yield
    • High equipment costs
    • Lower reaction rate
    • Catalyst poisoning

  17. For an exothermic reaction, what happens to the value of Kc when temperature increases?

    • Doubles
    • Increases
    • Stays the same
    • Decreases

  18. Which change shifts the position of equilibrium towards products for an exothermic reaction?

    • Adding a catalyst
    • Increasing volume
    • Raising temperature
    • Lowering temperature

  19. What does a Kc value close to 1 indicate about an equilibrium mixture?

    • Mostly reactants
    • Mostly products
    • Comparable amounts
    • No products

  20. What happens to the position of equilibrium when an inert gas is added at constant volume?

    • Shifts to products
    • Remains unchanged
    • Shifts to reactants
    • Oscillates continuously

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