Lesson 3.1.5.5

3.1.5.5 Catalysts Quiz: AQA Chemistry, Unit 1

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 3.1.5.5, Catalysts: 20 multiple choice questions for the AQA Chemistry (7405), Unit 1: Physical chemistry, written with Revision Ninja.

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The 20 questions

  1. What happens to the chemical composition of a catalyst during a reaction?

    • Decomposes fully
    • Oxidises completely
    • Remains unchanged
    • Reacts permanently

  2. How does a catalyst increase the rate of a chemical reaction?

    • Increasing particle energy
    • Increasing collision frequency
    • Lowering activation energy
    • Increasing activation energy

  3. On a Maxwell–Boltzmann curve, what is altered by adding a catalyst?

    • Most probable energy
    • Total curve area
    • Peak height position
    • Activation energy position

  4. How does adding a catalyst affect the overall enthalpy change of a reaction?

    • Reverses enthalpy sign
    • No effect
    • Increases enthalpy change
    • Decreases enthalpy change

  5. What effect does a catalyst have on the activation energy of a reverse reaction?

    • Prevents reaction
    • Lowers it
    • No effect
    • Increases it

  6. At 300 K, the uncatalysed activation energy is 80 kJ/mol and the catalysed value is 50 kJ/mol. Using k = Ae^(-Ea/RT) with the same A and R = 8.314 J/(K mol), roughly how many times faster is the catalysed reaction?

    • About 1.7 x 10^5 times faster
    • About 1.7 x 10^2 times faster
    • About 3.0 x 10^1 times faster
    • About 1.2 x 10^1 times faster

  7. Why does a lower activation energy increase reaction rate on a Maxwell–Boltzmann distribution?

    • Increased total area
    • Shifted curve peak
    • More successful collisions
    • Higher particle speeds

  8. What is a main practical advantage of using a heterogeneous solid catalyst?

    • Permanent consumption
    • Higher yield
    • Increased pressure
    • Easy separation

  9. How does the mass of a catalyst at the end of a reaction compare to the start?

    • It is identical
    • It is halved
    • It is doubled
    • It is zero

  10. Which feature on a reaction profile diagram is lower for a catalysed reaction?

    • Energy barrier peak
    • Product energy level
    • Overall enthalpy change
    • Reactant energy level

  11. At 298 K, reducing the activation energy from 60 to 40 kJ/mol with A unchanged raises the rate by a factor of about how much? Use RT = 2478 J/mol.

    • About 3.2 x 10^3
    • About 1.5 x 10^2
    • About 3.2 x 10^1
    • About 6.0 x 10^4

  12. In the Arrhenius equation, k = A e^(-Ea/RT), how does a catalyst increase rate constant k?

    • By increasing T
    • By increasing Ea
    • By decreasing Ea
    • By decreasing A

  13. A reaction has Ea = 100 kJ/mol. A catalyst lowers it to 75 kJ/mol at the same temperature. Which expression gives the ratio of the catalysed rate constant to the uncatalysed rate constant?

    • exp(100000/(RT)) minus exp(75000/(RT))
    • exp(25000/(RT))
    • 25000/(RT)
    • exp(-25000/(RT))

  14. What term describes gas molecules binding to the surface of a solid catalyst?

    • Adsorption
    • Absorption
    • Dissolution
    • Desorption

  15. Which of the following changes will NOT increase the rate of a chemical reaction?

    • Increasing surface area
    • Increasing concentration
    • Adding a catalyst
    • Decreasing temperature

  16. At 400 K, lowering the activation energy from 90 to 60 kJ/mol with A unchanged increases the rate by about what factor? Use RT = 3326 J/mol.

    • About 3.0 x 10^2
    • About 8.3 x 10^3
    • About 2.0 x 10^5
    • About 8.3 x 10^1

  17. Two catalysts act on the same reaction at 300 K. Catalyst X lowers the activation energy by 10 kJ/mol more than catalyst Y. Assuming the rate ratio depends only on exp(10000/RT) with RT = 2494 J/mol, roughly how much faster is X?

    • About 4 times faster
    • About 2500 times faster
    • About 10 times faster
    • About 55 times faster

  18. At 300 K, what fraction of molecules has energy at least equal to an activation energy of 50 kJ/mol, using exp(-Ea/RT) with R = 8.314 J/(K mol)?

    • About 2.0 x 10^-4
    • About 2.0 x 10^-9
    • About 1.0 x 10^-20
    • About 5.0 x 10^-1

  19. Which term describes the ability of an enzyme to catalyse only one specific reaction?

    • Saturation
    • Inhibition
    • Specificity
    • Denaturation

  20. Why is a catalyst used when operating an exothermic process at lower temperatures?

    • To decrease yield
    • To increase enthalpy
    • To maintain rate
    • To shift equilibrium

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