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

In partnership with Revision Ninja

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

Host it live on the board and students join with a game code on their own devices, or revise alone with Free Play. The answers are revealed in the game.

Host this setFree Play

The 20 questions

  1. What is the defining property of a catalyst in a chemical reaction?

    • It increases the equilibrium yield of product and is used up in the reaction
    • It increases the enthalpy change of the reaction and is converted into product
    • It increases the rate of a reaction and is chemically unchanged at the end of it
    • It lowers the rate of a reaction by stabilising the reactants in a fixed composition

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

    • By increasing the activation energy of the forward reaction only
    • By raising the temperature of the reacting mixture above the set value
    • By providing an alternative reaction route with a lower activation energy
    • By increasing the enthalpy change of the reaction so more energy is released

  3. On a Maxwell-Boltzmann distribution, what does a catalyst change at a fixed temperature?

    • The position of the peak, moving it to a higher temperature on the graph
    • The total area under the curve, so more molecules exist in the mixture
    • The total number of molecules that have energy above zero
    • The activation energy, so a larger area under the curve lies beyond it

  4. Which statement about a catalyst and the enthalpy change of a reaction is correct?

    • A catalyst changes the enthalpy change only when the reaction is endothermic
    • A catalyst does not change the enthalpy change of the reaction
    • A catalyst makes the enthalpy change more exothermic by its own energy
    • A catalyst lowers the enthalpy change by the amount of activation energy saved

  5. A catalyst lowers the activation energy for a reaction. What does this do to the activation energies of the forward and reverse reactions?

    • It raises both activation energies by the same amount to keep the rate steady
    • It lowers both the forward and the reverse activation energies
    • It raises the reverse activation energy and lowers the forward one
    • It lowers only the forward activation energy and leaves the reverse unchanged

  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. A reaction is carried out at a fixed temperature, and a catalyst is added. Which explanation for the faster rate, based on a Maxwell-Boltzmann distribution, is correct?

    • The curve becomes steeper, so the molecules travel faster and collide more often
    • The total area under the curve increases, meaning more molecules are present in the vessel
    • More molecules have energy at or above the lower activation energy, shown by a larger area beyond it
    • The peak of the distribution moves to higher energy, so molecules collide with more energy

  8. In the Haber process, solid iron is used as a catalyst. Which statement explains a practical advantage of a heterogeneous catalyst such as this?

    • The solid is consumed slowly so the product is contaminated with metal atoms each cycle
    • The solid dissolves the gases so that they react throughout the whole of the liquid phase
    • The solid raises the temperature of the gases so that the equilibrium yield increases
    • The reaction takes place on its surface and the solid catalyst can be separated from the gas mixture

  9. A catalyst is added to the reaction A + B to give C. After the reaction finishes, how much catalyst is left compared with the start?

    • The same amount as at the start, because it is regenerated in the reaction cycle
    • More than the original amount, because the catalyst is itself a product of the reaction
    • None, because all of the catalyst is consumed in forming the product molecules
    • Half of the original amount, because half of it has been used up in the reaction

  10. Which feature of an energy profile diagram shows that a reaction has been catalysed?

    • A lower peak, showing a lower activation energy between the same reactant and product energy levels
    • Reactant and product energy levels that are different from the uncatalysed reaction
    • A peak of the same height but moved to the right, showing a longer reaction time
    • A higher peak, showing that more energy is needed to start the reaction

  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. Which equation describes how the rate constant k depends on temperature and activation energy, and what the catalyst changes in it?

    • k = A/(RT): a catalyst lowers the temperature, which increases the value of k
    • k = Ae^(Ea/RT): a catalyst raises Ea, so k increases as the temperature falls
    • k = Ae^(-Ea/RT): a catalyst lowers Ea, so the exponential term and k increase
    • k = Ea/(RT): a catalyst increases the Arrhenius constant A, which raises k

  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. Platinum in a catalytic converter converts carbon monoxide to carbon dioxide. Why is the metal surface important to its action?

    • Gas molecules adsorb onto its large surface area, which weakens bonds and lowers the activation energy
    • The gases dissolve into the metal so that no gas remains in the exhaust after treatment
    • The metal heats the gas molecules to high speeds, so they collide more often on the surface
    • Platinum forms a stable bond with carbon dioxide, which removes the product from the mixture

  15. Which change would not increase the rate of a reaction, as explained by collision theory and the Maxwell-Boltzmann distribution?

    • Increasing the concentration of the gaseous reactants in a closed vessel
    • Increasing the surface area of a solid catalyst that is exposed to the reactants
    • Raising the temperature of the reacting mixture at the same pressure
    • Using a catalyst whose alternative route has a higher activation energy than the uncatalysed route

  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 statement about enzymes, which are biological catalysts, is correct?

    • Enzymes are used up in every reaction and must be continually replaced in the cell
    • Enzymes work best at very high temperatures, above 100 C, in all living cells
    • Enzymes are usually highly specific, acting on one substrate or a closely related type of reaction
    • Enzymes change the enthalpy change of the reactions they catalyse in the cell

  20. A company says a catalyst lets it run an exothermic reversible reaction at a lower temperature, avoiding the energy cost of heating. What is the main trade-off to evaluate?

    • A lower temperature always gives a higher rate, so the catalyst is unnecessary in every case
    • The catalyst is consumed quickly, so the company must reheat the reactor to restore its activity
    • A lower temperature may keep yield high for an exothermic reaction, but the rate must still be acceptable
    • A catalyst raises the equilibrium yield of an exothermic reaction, so temperature is irrelevant

All AQA Chemistry quizzes