Lesson 5.6.2.5

5.6.2.5 The effect of changing concentration (HT only) Quiz: AQA Combined Science, Unit 13

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 5.6.2.5, The effect of changing concentration (HT only): 20 multiple choice questions for the AQA GCSE Combined Science (8464), Unit 13: The rate and extent of chemical change, written with Revision Ninja.

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The 20 questions

  1. When reactant concentration increases at equilibrium, when do concentration changes stop?

    • Pressure drops
    • Equilibrium reached
    • Catalyst added
    • Reaction stops

  2. If product concentration is decreased, more reactants react until when?

    • Reaction stops
    • Equilibrium reached
    • All reactants gone
    • Temperature drops

  3. What state is an equilibrium system in immediately after a concentration is changed?

    • Completely stopped
    • At maximum yield
    • Not at equilibrium
    • At dynamic equilibrium

  4. Adding more of reactant A to A + B to C + D shifts the position:

    • Towards C and D
    • Towards A and B
    • Not at all
    • Towards a catalyst

  5. Removing product D from A + B to C + D: which reactants are consumed?

    • A and B
    • C and D
    • Only B
    • Only A

  6. Increasing the concentration of product C shifts the position:

    • Not at all
    • Towards D only
    • Towards A and B
    • Towards C and D

  7. What effect does changing reactant concentration have on the equilibrium constant?

    • Stops it
    • Decreases it
    • Increases it
    • No effect

  8. In reaction A + B <=> C + D, what does increasing concentration of B cause?

    • More C and D
    • More reactants
    • No change
    • Less product

  9. Which change would decrease the amount of product C at equilibrium?

    • Adding more D
    • Adding more B
    • Adding more A
    • Removing D

  10. What is the effect of adding a catalyst on equilibrium concentrations?

    • No change
    • Increases reactants
    • Doubles yield
    • Increases products

  11. Adding B to A + 2B to C shifts equilibrium:

    • Away from C
    • Towards C
    • Not at all
    • Towards A only

  12. What happens if a product is continually removed from an equilibrium mixture?

    • More product forms
    • Temperature drops
    • Reaction stops
    • Reactants increase

  13. Adding reactant A to equilibrium: which substance's concentration increases?

    • The solvent only
    • Nothing changes
    • A catalyst
    • Product C

  14. A reactant concentration decreases. The equilibrium shifts:

    • Not at all
    • Towards the products
    • Towards the catalyst
    • Towards the reactants

  15. For 2X + Y to 3Z, if Z is increased, the equilibrium shifts:

    • Towards X and Y
    • Towards neither side
    • Towards Z
    • Not at all

  16. Why does changing concentration alter the position of equilibrium?

    • To consume catalysts
    • To change temperature
    • To stop collisions
    • To re-balance rates

  17. When reactant B is added to A + B <=> C + D at equilibrium, what happens to C?

    • Increases
    • Drops to zero
    • Decreases
    • Stays constant

  18. Which side does an equilibrium system move towards when a substance is added?

    • Side removing it
    • Unchanged side
    • Faster side
    • Side adding it

  19. What happens to product concentration immediately after a reactant's concentration is doubled?

    • Drops to zero
    • Stays the same
    • Doubles instantly
    • Halves instantly

  20. What are the concentrations reached after a system shifts to counteract a change called?

    • Initial rate
    • Activation point
    • Maximum yield
    • New equilibrium

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