3.1.5.3 Effect of temperature on reaction rate Quiz: AQA Chemistry, Unit 1

The 20 questions

1. What is the qualitative effect of raising the temperature on reaction rate?

   • It has no effect on the rate
   • It increases the rate
   • It decreases the rate
   • It only increases the activation energy

2. Why does raising temperature increase the rate of reaction?

   • The activation energy increases with temperature, so particles need more energy to react together
   • The enthalpy change becomes more negative as temperature rises, releasing energy more quickly
   • Particles become heavier as they are heated, so they collide more forcefully with each other
   • More collisions have energy at or above the activation energy, and collisions are more frequent

3. As a rough rule, how does the rate of many reactions change for a 10 K rise in temperature?

   • It roughly doubles
   • It halves
   • It is unaffected
   • It increases by a factor of 100

4. In the sodium thiosulfate and hydrochloric acid experiment, what is typically measured to find the initial rate?

   • The temperature of the flask only, recorded at regular intervals during the reaction
   • The mass of solid precipitate formed, weighed at the end of the reaction in the flask
   • The volume of hydrogen collected in a gas syringe during the reaction over time
   • The time for a cross beneath the flask to disappear, with rate taken as 1/time

5. Which variable must be kept constant when investigating the effect of temperature on rate?

   • The concentration of the reactants
   • The temperature of the reactant solution
   • The time for the reaction to be recorded
   • The mass of product formed at the end

6. In the thiosulfate and acid experiment investigating temperature, which variable is changed?

   • The volume of hydrochloric acid only
   • The temperature of the reactant solution
   • The colour of the solution
   • The mass of the flask

7. Which statement about the effect of temperature on activation energy is true?

   • Activation energy doubles for every 10 K rise
   • Activation energy is zero above 100 C
   • Activation energy falls as temperature rises
   • Activation energy is unchanged by a temperature change

8. A reaction has a rate of 1.0 at 20 C and roughly doubles for every 10 K. What is the rate at 30 C?

   • 10
   • 0.5
   • 1.0
   • 2.0

9. Using the same rule, what is the rate at 40 C if the rate is 1.0 at 20 C?

   • 8.0
   • 4.0
   • 1.5
   • 2.0

10. A cross takes 40 s to disappear at 20 C. If the rate doubles at 30 C, what is the new time?

    • 20 s, because the rate doubles and the time halves
    • 40 s, because the time is unchanged by a change in temperature here
    • 80 s, because the rate halves so the time doubles in the same way
    • 400 s, because the time is multiplied by ten for each 10 K rise

11. In the thiosulfate experiment, rate is proportional to 1/time. If the time falls from 80 s to 20 s, by what factor does the rate increase?

    • Four times
    • The rate is unchanged
    • Two times
    • Ten times

12. A reaction rate is 0.020 mol dm-3 s-1 at 25 C and 0.040 mol dm-3 s-1 at 35 C. What is the approximate factor increase per 10 K?

    • About 2
    • About 4
    • About 0.5
    • No change

13. Why is the reaction flask placed in a water bath in initial rate experiments?

    • To change the activation energy
    • To make the reaction exothermic
    • To speed up the reaction by adding energy continuously
    • To keep the temperature constant and controlled

14. A student expects doubling the temperature to double the rate exactly. Which is the best response?

    • Yes, the rate always doubles exactly, because each extra kelvin adds the same fixed proportion to the rate
    • That is not exact, because the increase depends on how the fraction of molecules above the activation energy changes
    • Yes, because the activation energy doubles whenever the temperature is doubled in kelvin, so the rate doubles too
    • No, the rate falls with temperature, because particles collide more gently and less often when they are warmer

15. Which apparatus is commonly used to measure the volume of gas produced in a rate experiment?

    • A thermometer only
    • A burette only
    • A pipette only
    • A gas syringe

16. Why does a small rise in temperature cause a large increase in rate?

    • The activation energy is halved by the small rise, so far more collisions become successful
    • A small rise shifts the curve so a much larger fraction of molecules have energy above the activation energy
    • The rate doubles because the pressure of the gas rises in proportion to the temperature rise
    • The mass of the molecules falls as they warm, so they move more quickly and collide more

17. Rates measured at 25 C and 35 C are in the ratio 2 : 1. Which explanation is best?

    • Activation energy falls as temperature rises, so a larger share of collisions has enough energy to react at all
    • Activation energy is only defined at one temperature, so rates measured at different temperatures cannot be compared fairly
    • Temperature increases the fraction of collisions with energy at or above the activation energy, not the activation energy itself
    • Activation energy increases to match the temperature, so the reaction needs more energy to start overall

18. A reaction takes 60 s at 25 C and 15 s at 45 C. How do the rates compare?

    • The same rate at both
    • Two times faster at 45 C
    • Four times faster at 45 C
    • Four times slower at 45 C

19. In an experiment, the rate at 300 K is 0.010 and at 310 K is 0.020. What is the ratio of rates for each 10 K rise?

    • 0.5
    • 1
    • 10
    • 2

20. What must stay the same for a fair comparison of rates at two temperatures?

    • The concentrations and volumes of the reactants
    • Different concentrations at each temperature
    • Different catalysts used at each temperature
    • Different volumes at the same temperature

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