Lesson 16.1.4

16.1.4 Reaction mechanisms and the rate-determining step Quiz: Pearson Edexcel Chemistry, Unit 16

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 16.1.4, Reaction mechanisms and the rate-determining step: 20 multiple choice questions for the Pearson Edexcel Chemistry (9CH0), Unit 16: Kinetics II, written with Revision Ninja.

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The 20 questions

  1. What is the rate-determining step in a multi-step reaction mechanism?

    • The fastest step
    • The initial step
    • The slowest step
    • The final step

  2. Which species can appear in the rate equation for a chemical reaction?

    • Intermediates only
    • Reactants and catalysts
    • Products only
    • Products and intermediates

  3. Why can reaction intermediates never appear in the overall rate equation?

    • They are reactants
    • They have zero order
    • They are catalysts
    • They cancel out

  4. In the acid-catalysed iodination of propanone, what is the order with respect to iodine?

    • 0
    • 2
    • 1
    • -1

  5. What is the order with respect to H+ in the acid-catalysed iodination of propanone?

    • 1/2
    • 2
    • 0
    • 1

  6. Which type of halogenoalkane hydrolysis follows the rate equation rate = k[halogenoalkane]?

    • Tertiary SN1
    • Secondary SN2
    • Primary SN1
    • Primary SN2

  7. For 2NO + O2 -> 2NO2 with rate = k[NO]^2[O2], what is the overall order?

    • 1
    • 3
    • 2
    • 4

  8. A mechanism has step 1 (slow): A + B -> X, and step 2 (fast): X + C -> D. Which rate equation is consistent?

    • rate = k[A][B][C]
    • rate = k[A][B]
    • rate = k[X][C]
    • rate = k[D]

  9. If rate = k[NO2]^2, how many NO2 molecules are in the rate-determining step?

    • Zero
    • One
    • Three
    • Two

  10. If a reaction has rate equation rate = k[A]^2, what is involved in the slow step?

    • One A molecule
    • Two A molecules
    • Two A and B
    • One B molecule

  11. For SN2 hydrolysis of a primary halogenoalkane in a single step, which rate equation applies?

    • rate = k[halogenoalkane]
    • rate = k[OH-]
    • rate = k[halogenoalkane]^2
    • rate = k[halogenoalkane][OH-]

  12. Which species is involved in the slow rate-determining step of an SN1 reaction?

    • Halogenoalkane only
    • Halogenoalkane and hydroxide
    • Hydroxide ion only
    • Carbocation only

  13. On a reaction profile with multiple steps, which step is the rate-determining step?

    • Highest activation energy
    • Most exothermic step
    • Highest enthalpy change
    • Lowest activation energy

  14. When will a catalyst appear in the rate equation of a reaction?

    • Never appears
    • In fast step
    • In products only
    • In slow step

  15. Why does the stoichiometric equation not necessarily match the rate equation orders?

    • Multi-step mechanism
    • Products affect rate
    • Single collision step
    • Catalysts change orders

  16. In the acid-catalysed iodination of propanone, rate = k[propanone][H+]. What role does iodine play?

    • Fast step reactant
    • Homogeneous catalyst
    • Inhibitor
    • Slow step reactant

  17. A reaction has rate = k[NO]^2[H2]. Which species react in the rate-determining step?

    • Two H2 only
    • Two NO and 2 H2
    • Two NO and H2
    • One NO and H2

  18. Hydrolysis rate of 2-bromo-2-methylpropane is independent of [OH-]. Which mechanism occurs?

    • SN1 mechanism
    • Electrophilic addition
    • Nucleophilic addition
    • SN2 mechanism

  19. A reaction has the rate equation rate = k[A][B]². What species are present in or before the rate-determining step?

    • One A, one B
    • One A, two B
    • Two A, two B
    • Two A, one B

  20. What term describes a species formed in one step of a mechanism and consumed in a later step?

    • Free radical
    • Catalyst
    • Transition state
    • Intermediate

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