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Reaction rates and the Boltzmann distribution

Past-paper questions pack

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Questions are numbered; the mark schemes (the answer key) follow on separate pages so the question pages can be handed out alone. www.chemistryaleveltutor.com

OCR AS and A-level Chemistry past-paper questions since 2016 · 60 parts · mark schemes follow the questions · www.chemistryaleveltutor.com · Questions and mark schemes © OCR

1. June 2025 · Paper 1 · Q5 · 1 marks ·
5 The graph shows the volume of hydrogen released over time in a chemical reaction. 100 90 80 70 60 Volume of hydrogen 50 / cm3 40 30 20 10 0 0 20 40 60 80 100 Time / s What is the rate of reaction, in cm3 s–1, at 30 seconds? A 0.8 B 1.2 C 2.1 D 2.4 Your answer [1]
2. June 2025 · AS Paper 1 · Q12 · 1 marks ·
12 Hydrogen and iodine react in the reaction below. H2(g) + I2(g) 2HI(g) Which row is correct when pressure is increased? Rate of reaction Equilibrium yield of HI A Increases Increases B Increases No effect C Increases Decreases D Decreases No effect Your answer [1]
3. June 2025 · AS Paper 1 · Q13 · 1 marks ·
13 Which statement is not a sustainability benefit of an industrial process using a catalyst? A Lower temperatures can be used. B The position of equilibrium moves towards the products. C The reaction takes place in less time. D There is reduced energy demand. Your answer [1]
4. June 2025 · Paper 1 · Q18(a)(i) · 1 marks ·
18 Nitrogen monoxide, NO, reacts with oxygen to form nitrogen dioxide, NO2. 2NO(g) + O2(g) 2NO2(g) Reaction 18.1 (a) The rate of reaction increases in the presence of a heterogeneous platinum catalyst. (i) Explain why platinum is an example of a heterogeneous catalyst for Reaction 18.1. .......................................................................................................................................................... ..................................................................................................................................................... [1]
5. June 2025 · Paper 1 · Q18(a)(ii) · 2 marks ·
(ii) Explain how the platinum catalyst increases the rate of reaction. Include a labelled sketch of the Boltzmann distribution on the grid. Number of molecules 0 0 Energy .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... ..................................................................................................................................................... [2]
6. June 2025 · Paper 1 · Q18(a)(iii) · 1 marks ·
(iii) In industry, catalysts have great economic importance and benefits for increased sustainability. Explain how the use of catalysts is beneficial to the environment. .......................................................................................................................................................... .......................................................................................................................................................... ..................................................................................................................................................... [1]
7. June 2025 · AS Paper 1 · Q21(d)(ii) · 3 marks ·
(ii) Explain the shape of the graph in Fig. 21.1, in terms of concentration, collisions and time. .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .................................................................................................................................................... [3]
8. June 2024 · Paper 1 · Q8 · 1 marks ·
8 Which row in the table explains how a catalyst affects the activation energy (Ea) and the proportion of molecules with energy > Ea? How the activation Proportion of molecules energy changes with energy > Ea A decreases decreases B decreases increases C increases decreases D increases increases Your answer [1]
9. June 2024 · AS Paper 1 · Q12 · 1 marks ·
12 A mixture of gases is heated in a closed container. The reaction rate increases. Which statement explains why the rate increases? A More molecules have an energy greater than the activation energy. B The activation energy decreases. C The activation energy increases. D The concentration of the gases increases. Your answer [1]
10. June 2024 · Paper 1 · Q16(b)(i) · 3 marks ·
(b) The rate of decomposition of hydrogen peroxide shown in Reaction 16.1 can be increased by adding a small amount of powdered manganese(IV) oxide, MnO2. The MnO2 acts as a catalyst. (i) Complete the enthalpy profile diagram for Reaction 16.1 using formulae for the reactants and products. • Use Ea to label the activation energy without MnO2. • Use Ec to label the activation energy with MnO2. • Use ∆H to label the enthalpy change of reaction. enthalpy progress of reaction [3]
11. June 2024 · Paper 1 · Q16(b)(ii) · 1 marks ·
(ii) Explain why MnO2 is described as a heterogeneous catalyst for this reaction. .......................................................................................................................................................... ..................................................................................................................................................... [1]
12. June 2024 · Paper 1 · Q17(a) · 1 marks ·
17 Crystal violet (CV) is a purple dye. In the presence of an alkali, CV reacts to form a colourless product. A student uses a colorimeter to investigate the rate of the reaction between CV and sodium hydroxide, NaOH. • The student mixes 10.0 cm3 of 2.8 × 10–7 mol dm–3 CV with 10.0 cm3 of 0.016 mol dm–3 NaOH. • A large excess of NaOH is used, so that the reaction is effectively zero-order with respect to OH– ions. • The student places a sample of the reaction mixture in a colorimeter and measures the absorbance over time. The student uses the absorbance readings to calculate the concentration of CV and plots a graph of concentration of CV against time, as shown below. 1.6 × 10–7 1.4 × 10–7 1.2 × 10–7 1.0 × 10–7 concentration of CV 0.8 × 10–7 / mol dm–3 0.6 × 10–7 0.4 × 10–7 0.2 × 10–7 0 0 1 2 3 4 5 6 7 8 9 10 time / min (a) Using collision theory, explain why the gradient decreases over time. .......................................................................................................................................................... .......................................................................................................................................................... ..................................................................................................................................................... [1]
13. June 2024 · AS Paper 2 · Q4(a) · 4 marks ·
4 Aqueous hydrogen peroxide, H2O2(aq), gradually decomposes to produce water and oxygen. 2H2O2(aq) 2H2O(l) + O2(g) ΔH = –196 kJ mol–1 Equation 4.1 The rate of decomposition of H2O2 can be increased by adding a small amount of manganese(IV) oxide, MnO2, which acts as a catalyst. (a) Explain, using a Boltzmann distribution model, why the rate of a reaction increases in the presence of a catalyst. You are provided with the axes below, which you should label. .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... ..................................................................................................................................................... [4]
14. June 2024 · AS Paper 2 · Q4(b)(ii) · 2 marks ·
(ii) Use your graph to determine the rate of reaction, in cm3 s–1, at 50 s. Show your working below and on the graph. rate = ............................................. cm3 s–1 [2]
15. June 2023 · AS Paper 1 · Q13 · 1 marks · AO1
13 The Boltzmann distribution showing the activation energy, Ea, for an uncatalysed reaction is shown below. number of molecules Ea energy What is the difference for the catalysed reaction? A The activation energy shifts to the left. B The activation energy shifts to the right. C The curve flattens. D The curve shifts to the right. Your answer [1]
16. June 2023 · AS Paper 1 · Q14 · 1 marks · AO2
14 A student measures how the OH– concentration changes over time for a reaction. The student plots the graph below. 0.20 0.15 [OH–(aq)] 0.10 / mol dm–3 0.05 0.00 0 100 200 300 400 500 600 time / s What is the rate of reaction, in mol dm–3 s–1, at 200 s? A 2.2 × 10–4 B 2.8 × 10–4 C 1.8 × 10–3 D 4.4 × 10–2 Your answer [1]
17. June 2023 · Paper 1 · Q20(d)(ii) · 3 marks · AO1, 3
(ii) Explain why these two reactions of magnesium produce the same volume of gas but at different rates. ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ...................................................................................................................................... [3]
18. June 2023 · AS Paper 1 · Q23(a)(iii) · 2 marks · AO1
(iii) CO and NO are removed by use of a catalyst. Explain the role of the catalyst. Refer to your enthalpy profile diagram in Fig. 23.1 in your answer. ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ...................................................................................................................................... [2]
19. June 2022 · Paper 1 · Q16(a)(i) · 3 marks · AO1
SECTION B Answer all the questions. 16 A catalytic converter in a car removes nitrogen monoxide, NO, and carbon monoxide, CO, from the exhaust gases. (a) One reaction that happens in a catalytic converter is shown below. 2CO(g) + 2NO(g) N2(g) + 2CO2(g) Reaction 16.1 (i) Explain how increasing the temperature increases the rate of Reaction 16.1. Include a labelled sketch, using Boltzmann distributions, on the grid below. Label the axes. ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ...................................................................................................................................... [3]
20. June 2022 · AS Paper 1 · Q25(b) · 3 marks · AO1
(b) The Boltzmann distribution model can be used by chemists to explain how the rate of a reaction is affected by temperature. Fig. 25.1 shows the Boltzmann distribution for a gas at room temperature. Fig. 25.1 Label the axes on Fig. 25.1 and add a second curve to show the Boltzmann distribution of the gas at a higher temperature. Explain why the Boltzmann distribution shows that the rate of a reaction is affected by temperature. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... .............................................................................................................................................. [3]
21. June 2022 · AS Paper 2 · Q3(a)(i) · 3 marks · AO1, 2
3 A student investigates some reactions of zinc compounds and zinc metal. (a) The student investigates the rate of reaction between zinc carbonate, ZnCO3(s), and dilute hydrochloric acid, HCl (aq). ZnCO3(s) + 2HCl (aq) ZnCl 2(aq) + CO2(g) + H2O(l) The student follows the method outlined below: • Add 50 cm3 of dilute HCl (aq) into a conical flask at 20 °C. • Place the flask on a top-pan balance. • Add an excess of ZnCO3(s) to the flask. • Record the mass of the flask and contents on the top-pan balance every 30 seconds. The student plots a graph of mass against time, shown in Fig. 3.1 below. 92.6 92.5 92.4 92.3 92.2 92.1 92.0 91.9 mass / g 91.8 91.7 91.6 91.5 91.4 91.3 91.2 91.1 91.0 0 50 100 150 200 250 300 350 400 time / s Fig. 3.1 (i) The graph shows that the reaction gets slower over time, and eventually stops. Explain why, in terms of collision theory. ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ...................................................................................................................................... [3]
22. June 2022 · AS Paper 2 · Q3(a)(ii) · 2 marks · AO3
(ii) Using the graph in Fig. 3.1, find the rate of reaction, in g s–1, at 50 seconds. Show your working on the graph and in the space below. rate of reaction = ................................................. g s–1 [2]
23. June 2022 · AS Paper 2 · Q3(a)(iii) · 2 marks · AO3
(iii) The student repeats the experiment but heats 50 cm3 of dilute hydrochloric acid up to 40 °C before adding the ZnCO3(s). On Fig. 3.1, sketch the curve the student would obtain. [2]
24. June 2022 · AS Paper 2 · Q3(b)(i) · 2 marks · AO2
(b) The student investigates the reaction between zinc and dilute sulfuric acid. Zn(s) + H2SO4(aq) ZnSO4(aq) + H2(g) ΔH = –140 kJ mol–1 Copper(II) sulfate is a catalyst for this reaction. • The student adds a piece of zinc to each of two test tubes. • The student adds a few drops of aqueous copper(II) sulfate to one of the test tubes, forming a pale blue solution. • The student adds an excess of dilute sulfuric acid to each test tube. (i) Describe two differences the student would observe between the test tubes. 1 ........................................................................................................................................ ........................................................................................................................................... 2 ........................................................................................................................................ ........................................................................................................................................... [2]
25. June 2022 · AS Paper 2 · Q3(b)(ii) · 3 marks · AO1, 2
(ii) Using the axes below, sketch an enthalpy profile diagram for the reaction with and without the catalyst. On your diagram, include the following labels: • ΔH, the enthalpy change • Ea, the activation energy without a catalyst • Ec, the activation energy with a catalyst. Enthalpy Zn(s) + H2SO4(aq) Progress of reaction [3]
26. June 2022 · AS Paper 2 · Q4(a)(i) · 6 marks · AO1, 2
4 This question is about the manufacture of hydrogen, H2. (a) In industry, hydrogen is manufactured from methane, as shown in Equilibrium 4.1. CH4(g) + H2O(g) CO(g) + 3H2(g) ΔH = +206 kJ mol–1 Equilibrium 4.1 The industrial process is carried out at 15 atmospheres pressure and at a temperature of 800 °C using an excess of steam. A nickel catalyst is used. (i)* Explain why these conditions are used industrially. [6] ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... Additional answer space if required. ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ...........................................................................................................................................
27. June 2022 · Paper 3 · Q4(a) · 4 marks · AO1, 2
4 Two students plan to investigate Equilibrium 4.1, shown below. CoCl 4 2−(aq) + 6H2O(l) [Co(H2O)6]2+(aq) + 4Cl −(aq) Equilibrium 4.1 blue pink (a) The students are supplied with the equilibrium mixture in Equilibrium 4.1 at room temperature. • One student heats 20 cm3 of the mixture to 50 °C. • The other student heats 20 cm3 of the mixture to 90 °C. The students use colorimetry to observe how the colour of the equilibrium mixture changes over time. • The colorimeter is set up so that the greater the absorbance, the greater the concentration of [Co(H2O)6]2+. • The initial absorbance is set to zero. • The absorbance is recorded every 30 seconds. The students plot the graph below from the results of the experiment. 50 °C 90 °C Absorbance 0,0 Time / s Use the graph and relevant chemical theory to answer the following. Include all reasoning: • Explain the different initial rates at 50 °C and 90 °C. • Predict the sign of ∆H for the forward reaction in Equilibrium 4.1. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... .............................................................................................................................................. [4]
28. November 2021 · AS Paper 1 · Q11 · 1 marks · AO1
11 The Boltzmann distributions below show a gas at two different temperatures. Which Boltzmann distribution shows the dotted curve at a higher temperature? number of A molecules energy number of B molecules energy number of C molecules energy number of D molecules energy Your answer [1]
29. November 2021 · Paper 1 · Q20(c)(ii) · 3 marks · AO1
(ii) The chemist then repeats the experiment three times. In each experiment, the chemist makes one change but uses the same initial amounts of NO and O2. Complete the table to show the predicted effect of each change compared with the original experiment. Only use the words greater, smaller or same. Equilibrium amount Change Kp Initial rate of NO2(g) Temperature increase Pressure increase Catalyst added [3]
30. November 2021 · AS Paper 1 · Q22(a) · 3 marks · AO1
22 This question is about enthalpy changes. Hydrogen, H2, can be manufactured by the reaction of methane and steam. This is a reversible reaction, as shown in Equilibrium 22.1 below. Equilibrium 22.1 CH4(g) + H2O(g) 3H2(g) + CO(g) ∆H = +206 kJ mol–1 (a) The rate of this reaction increases when a catalyst is present. Complete the enthalpy profile diagram below. On your diagram: • label the activation energies, Ea (without catalyst) and Ec (with catalyst) • label the enthalpy change of reaction, ∆H. enthalpy CH4(g) + H2O(g) progress of reaction [3]
31. November 2021 · AS Paper 2 · Q5(c) · 2 marks · AO3
(c) The industrial manufacture of methanol has used a copper-based catalyst. Chemists have recently developed a new method for making methanol that uses a nickel- gallium catalyst. This allows methanol to be produced at a lower temperature than the old method. Suggest two reasons why using a lower temperature is beneficial to the environment. 1 ................................................................................................................................................ ................................................................................................................................................... 2 ................................................................................................................................................ ................................................................................................................................................... [2]
32. November 2021 · AS Paper 2 · Q6(a) · 3 marks · AO1, 2
6 A student investigates the rate of reaction between strontium and water. Sr(s) + 2H2O(l) Sr(OH)2(aq) + H2(g) The student’s method is shown below. • Pour 100 cm3 of water into a conical flask. • Add 0.26 g of strontium and quickly connect a 100 cm3 gas syringe. • Measure the volume of gas produced every 10 seconds until all the strontium has reacted. The student plots a graph of volume of gas produced against time as shown in Fig. 6.1. 80 70 60 50 volume of gas 40 produced / cm3 30 20 10 0 0 10 20 30 40 50 60 70 80 90 100 time / s Fig. 6.1 (a) Draw a best fit curve on Fig. 6.1. Use the graph to determine the rate of reaction, in cm3 s–1, at 50 s. Show your working below and on the graph. rate at 50 s ............................................. cm3 s–1 [3]
33. November 2021 · AS Paper 2 · Q6(b) · 2 marks · AO3
(b) A second student suggests that the experiment could be improved by measuring the loss in mass in the conical flask over time. The student places a conical flask containing 100 cm3 of water on a 2 decimal place balance, and then adds 0.26 g of strontium. The mass is recorded every 10 seconds. Suggest one advantage and one disadvantage of using this method compared to the gas collection method. Advantage: ............................................................................................................................... ................................................................................................................................................... Disadvantage: ........................................................................................................................... .............................................................................................................................................. [2]
34. November 2021 · AS Paper 2 · Q6(c)(ii) · 2 marks · AO3
(ii) The student observes that the rate of reaction for barium is different from the rate of reaction with strontium. On Fig. 6.1 sketch the graph the student would obtain using barium instead of strontium. [2]
35. November 2020 · Paper 1 · Q7 · 1 marks · AO1
7 The diagram represents a Boltzmann distribution curve of molecules at a given temperature. number of molecules energy Which statement for this Boltzmann distribution curve is correct at a higher temperature? A The peak increases in height and moves to the left. B The peak increases in height and moves to the right. C The peak decreases in height and moves to the left. D The peak decreases in height and moves to the right. Your answer [1]
36. November 2020 · Paper 1 · Q17(b) · 2 marks · AO1
(b) A catalyst is used in the production of methanol in equilibrium 1. State two ways that the use of catalysts helps chemical companies to make their processes more sustainable and less harmful to the environment. 1 ................................................................................................................................................ ................................................................................................................................................... 2 ................................................................................................................................................ ................................................................................................................................................... [2]
37. November 2020 · AS Paper 1 · Q24(b) · 5 marks · AO1
(b) The industrial manufacture of NH3 from N2 and H2 is carried out at an increased temperature and in the presence of a catalyst. Explain, using Boltzmann distributions, why increasing the temperature and using a catalyst both increase the reaction rate. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... .............................................................................................................................................. [5]
38. June 2019 · AS Paper 1 · Q12 · 1 marks · AO1
12 What is the main reason for the increase in reaction rate with increasing temperature? A The activation energy decreases. B The activation energy increases. C More molecules have an energy greater than the activation energy. D The molecules collide more frequently. Your answer [1]
39. June 2019 · Paper 1 · Q19(c)(i) · 4 marks · AO1
(c) Vanadium(V) oxide, V2O5(s), is used as a catalyst in equilibrium 1. 2SO2(g) + O2(g) 2SO3(g)      ∆H = −197 kJ mol−1 Equilibrium 1 (i) Explain how the presence of V2O5(s) increases the rate of reaction. Include a labelled sketch of the Boltzmann distribution, on the grid below. Label the axes. ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ...................................................................................................................................... [4]
40. June 2019 · Paper 1 · Q19(c)(ii) · 1 marks · AO1
(ii) Explain whether vanadium(V) oxide is acting as a homogeneous or heterogeneous catalyst. ........................................................................................................................................... ...................................................................................................................................... [1]
41. June 2019 · AS Paper 2 · Q4(b)(i) · 1 marks · AO2
(b) The student uses the apparatus in the diagram. 100 cm3 gas syringe The student’s method is outlined below: • Pour 50.0 cm3 of 0.100 mol dm–3 HCl into the conical flask. • Add 0.200 g of zinc (an excess), and quickly attach the delivery tube and gas syringe. • Measure the volume of gas collected every 20 seconds until the reaction stops. The student obtains the results shown in Table 4.1. Time / s 0 20 40 60 80 100 120 160 200 Volume of gas / cm3 0 16 27 37 39 50 53 58 58 Table 4.1 (i) On the graph paper in Fig. 4.1, label the x axis and plot the results in Table 4.1. [1]
42. June 2019 · AS Paper 2 · Q4(b)(iii) · 1 marks · AO3
(iii) Draw a best-fit smooth curve on the graph you have drawn in Fig. 4.1. [1]
43. June 2019 · AS Paper 2 · Q4(c) · 2 marks · AO2
80 70 60 50 volume 40 / cm3 30 20 10 0 Fig. 4.1 (c) The student repeats the experiment using: • zinc with the same mass (0.200 g) and same surface area • the same temperature and pressure • 40.0 cm3 of 0.125 mol dm–3 HCl, instead of 50.0 cm3 of 0.100 mol dm–3 HCl. On your graph in Fig. 4.1 sketch the curve you would expect in this experiment. [2]
44. June 2019 · AS Paper 2 · Q4(d) · 2 marks · AO1
(d) The graph shows that rate of reaction decreases over time. Explain why, in terms of collision theory. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... .............................................................................................................................................. [2]
45. June 2019 · AS Paper 2 · Q4(e)(i) · 2 marks · AO1
(e) (i) The rate of the reaction between zinc and hydrochloric acid can be increased using a solution of copper(II) sulfate as a catalyst. Explain how a catalyst increases the rate of reaction. ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ...................................................................................................................................... [2]
46. June 2019 · AS Paper 2 · Q4(e)(ii) · 1 marks · AO2
(ii) Why is it difficult to classify the solution of copper(II) sulfate as a homogeneous or heterogeneous catalyst in this reaction? ........................................................................................................................................... ........................................................................................................................................... ...................................................................................................................................... [1]
47. June 2018 · Paper 1 · Q14 · 1 marks · AO1
14 Which statement(s) explain(s) why reaction rates increase as temperature increases? 1 The activation energy is less. 2 Collisions between molecules are more frequent. 3 A greater proportion of molecules have energy greater than the activation energy. A 1, 2 and 3 B Only 1 and 2 C Only 2 and 3 D Only 1 Your answer [1]
48. June 2018 · Paper 1 · Q20(b) · 3 marks ·
(b) Hydrogen iodide, HI, is decomposed by heat into its elements: 2HI(g) H2(g) + I2(g) ∆H = +9.5 kJ mol–1 The decomposition is much faster in the presence of a platinum catalyst. Complete the enthalpy profile diagram for this reaction using formulae for the reactants and products. • Use Ea to label the activation energy without a catalyst. • Use Ec to label the activation energy with a catalyst. • Use ∆H to label the enthalpy change of reaction. enthalpy progress of reaction [3]
49. June 2018 · AS Paper 1 · Q23(b) · 4 marks ·
(b) Using the Boltzmann distribution model, explain how the rate of a reaction is affected by temperature. You are provided with the axes below, which should be labelled. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... .............................................................................................................................................. [4]
50. June 2018 · AS Paper 2 · Q4(c) · 5 marks ·
(c) Predict the conditions of temperature and pressure for a maximum equilibrium yield of nitrogen monoxide in equilibrium 4.1. • Explain your prediction in terms of le Chatelier’s principle. • State and explain how these conditions could be changed to achieve a compromise between equilibrium yield, rate and other operational factors. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... .............................................................................................................................................. [5]
51. June 2018 · AS Paper 2 · Q5(b) · 2 marks ·
(b) A student investigates the rate of reaction of 1-bromobutane with aqueous hydroxide ions. The graph shows how the hydroxide ion concentration, [OH–(aq)], changes during the reaction. 0.45 0.40 0.35 0.30 [OH–(aq)] 0.25 / mol dm–3 0.20 0.15 0.10 0.05 0.00 0 50 100 150 200 time / min Using the graph, calculate the rate of reaction, in mol dm–3 min–1, at 30 minutes. Show your working on the graph and in the space below. rate of reaction = ................................. mol dm–3 min–1 [2]
52. June 2018 · Paper 3 · Q2(a)(i) · 5 marks ·
2 This question looks at reactions of hydrogen peroxide and of cobalt(II) ions. (a) Aqueous hydrogen peroxide decomposes as shown in equation 2.1. 2H2O2(aq) → 2H2O(l) + O2(g) Equation 2.1 The reaction is catalysed by manganese(IV) oxide, MnO2. A student investigates the decomposition of a hydrogen peroxide solution as outlined below. • The student adds 50.00 cm3 of H2O2(aq) to a conical flask. • The student adds a small spatula measure of MnO2 and quickly connects the flask to a gas syringe. • The student measures the volume of oxygen every 200 seconds. Results Time/s Volume of O2/cm3 0 0 200 15 400 28 600 36 800 41 1000 46 1200 48 1400 50 (i) Process the results as outlined below. • On page 5, plot a graph of volume of O2 against time. • Use your graph to find the rate of the reaction, in cm3 s–1, at t = 500 s. Show your working on the graph and in the space below. rate = ..............................................cm3 s–1 [5]
53. June 2017 · Paper 1 · Q19(b) · 1 marks ·
(b) Suggest a different experimental method that would allow the rate of this reaction to be followed over time. ................................................................................................................................................... .............................................................................................................................................. [1]
54. June 2017 · AS Paper 1 · Q23(a) · 4 marks ·
23 Methanol can be prepared industrially by reacting carbon monoxide with hydrogen in the presence of a copper catalyst. This is a reversible reaction. CO(g) + 2H2(g) CH3OH(g) (a) Using the Boltzmann distribution model, explain why the rate of a reaction increases in the presence of a catalyst. You are provided with the axes below, which should be labelled. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... .............................................................................................................................................. [4]
55. June 2017 · AS Paper 1 · Q23(b) · 2 marks ·
(b) The reaction for the production of methanol in the presence of the copper catalyst is carried out at 200–300 °C. Explain why use of the catalyst reduces energy demand and benefits the environment. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... .............................................................................................................................................. [2]
56. June 2017 · AS Paper 2 · Q2 · 6 marks ·
2* A student was asked to carry out an experiment to determine the initial rate of reaction of zinc and hydrochloric acid. The student plans to collect a total of about 72 cm3 of hydrogen at RTP and to use an excess of zinc. The student selects the following apparatus: • the apparatus shown in the diagram • 100 cm3 measuring cylinder • stop clock • 2 decimal place balance 100 cm3 gas syringe Outline how the student could carry out the experiment and explain how the results could be processed graphically. Show all working in your calculations. .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... ..................................................................................................................................................... [6]
57. June 2016 · AS Paper 2 · Q5(a)(i) · 1 marks · AO3
12 5 A student investigates the reaction between strontium carbonate and dilute nitric acid. SrCO3 + 2HNO3 Sr(NO3)2 + CO2 + H2O The rate of reaction is determined from the loss in mass over a period of time. (a) (i) Explain why there is a loss in mass during the reaction. ........................................................................................................................................... ...................................................................................................................................... [1]
58. June 2016 · AS Paper 2 · Q5(b)(i) · 2 marks · AO2
(b) The student plots a graph of total mass (reagents + container) against time. 96.40 96.30 96.20 mass / g 96.10 96.00 95.90 0 50 100 150 200 250 300 350 400 time / s 13 (i) Describe and explain the change in the rate of the reaction during the first 200 seconds of the experiment. ........................................................................................................................................... ........................................................................................................................................... ...................................................................................................................................... [2]
59. June 2016 · AS Paper 2 · Q5(b)(ii) · 2 marks · AO3
(ii) Using the graph, calculate the rate of reaction, in g s–1, at 200 seconds. Show your working on the graph. rate of reaction = ................................................. g s–1 [2]
60. June 2016 · AS Paper 2 · Q5(c) · 3 marks · AO3
(c) Outline a method that could be used to obtain the results that are plotted on the graph. Your answer should include the apparatus required and the procedure for the experiment. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... .............................................................................................................................................. [3]

Mark schemes

1. June 2025 · Paper 1 · Q5
Mark scheme June 2025 Paper 1 Q5
2. June 2025 · AS Paper 1 · Q12
Mark scheme June 2025 Paper 1 Q12
3. June 2025 · AS Paper 1 · Q13
Mark scheme June 2025 Paper 1 Q13
4. June 2025 · Paper 1 · Q18(a)(i)
Mark scheme June 2025 Paper 1 Q18(a)(i)
5. June 2025 · Paper 1 · Q18(a)(ii)
Mark scheme June 2025 Paper 1 Q18(a)(ii)
6. June 2025 · Paper 1 · Q18(a)(iii)
Mark scheme June 2025 Paper 1 Q18(a)(iii)
7. June 2025 · AS Paper 1 · Q21(d)(ii)
Mark scheme June 2025 Paper 1 Q21(d)(ii)
8. June 2024 · Paper 1 · Q8
Mark scheme June 2024 Paper 1 Q8
9. June 2024 · AS Paper 1 · Q12
Mark scheme June 2024 Paper 1 Q12
10. June 2024 · Paper 1 · Q16(b)(i)
Mark scheme June 2024 Paper 1 Q16(b)(i)
11. June 2024 · Paper 1 · Q16(b)(ii)
Mark scheme June 2024 Paper 1 Q16(b)(ii)
12. June 2024 · Paper 1 · Q17(a)
Mark scheme June 2024 Paper 1 Q17(a)
13. June 2024 · AS Paper 2 · Q4(a)
Mark scheme June 2024 Paper 2 Q4(a)
14. June 2024 · AS Paper 2 · Q4(b)(ii)
Mark scheme June 2024 Paper 2 Q4(b)(ii)
15. June 2023 · AS Paper 1 · Q13
Mark scheme June 2023 Paper 1 Q13
16. June 2023 · AS Paper 1 · Q14
Mark scheme June 2023 Paper 1 Q14
17. June 2023 · Paper 1 · Q20(d)(ii)
Mark scheme June 2023 Paper 1 Q20(d)(ii)
18. June 2023 · AS Paper 1 · Q23(a)(iii)
Mark scheme June 2023 Paper 1 Q23(a)(iii)
19. June 2022 · Paper 1 · Q16(a)(i)
Mark scheme June 2022 Paper 1 Q16(a)(i)
20. June 2022 · AS Paper 1 · Q25(b)
Mark scheme June 2022 Paper 1 Q25(b)
21. June 2022 · AS Paper 2 · Q3(a)(i)
Mark scheme June 2022 Paper 2 Q3(a)(i)
22. June 2022 · AS Paper 2 · Q3(a)(ii)
Mark scheme June 2022 Paper 2 Q3(a)(ii)
23. June 2022 · AS Paper 2 · Q3(a)(iii)
Mark scheme June 2022 Paper 2 Q3(a)(iii)
24. June 2022 · AS Paper 2 · Q3(b)(i)
Mark scheme June 2022 Paper 2 Q3(b)(i)
25. June 2022 · AS Paper 2 · Q3(b)(ii)
Mark scheme June 2022 Paper 2 Q3(b)(ii)
26. June 2022 · AS Paper 2 · Q4(a)(i)
Mark scheme June 2022 Paper 2 Q4(a)(i)
27. June 2022 · Paper 3 · Q4(a)
Mark scheme June 2022 Paper 3 Q4(a)
28. November 2021 · AS Paper 1 · Q11
Mark scheme November 2021 Paper 1 Q11
29. November 2021 · Paper 1 · Q20(c)(ii)
Mark scheme November 2021 Paper 1 Q20(c)(ii)
30. November 2021 · AS Paper 1 · Q22(a)
Mark scheme November 2021 Paper 1 Q22(a)
31. November 2021 · AS Paper 2 · Q5(c)
Mark scheme November 2021 Paper 2 Q5(c)
32. November 2021 · AS Paper 2 · Q6(a)
Mark scheme November 2021 Paper 2 Q6(a)
33. November 2021 · AS Paper 2 · Q6(b)
Mark scheme November 2021 Paper 2 Q6(b)
34. November 2021 · AS Paper 2 · Q6(c)(ii)
Mark scheme November 2021 Paper 2 Q6(c)(ii)
35. November 2020 · Paper 1 · Q7
Mark scheme November 2020 Paper 1 Q7
36. November 2020 · Paper 1 · Q17(b)
Mark scheme November 2020 Paper 1 Q17(b)
37. November 2020 · AS Paper 1 · Q24(b)
Mark scheme November 2020 Paper 1 Q24(b)
38. June 2019 · AS Paper 1 · Q12
Mark scheme June 2019 Paper 1 Q12
39. June 2019 · Paper 1 · Q19(c)(i)
Mark scheme June 2019 Paper 1 Q19(c)(i)
40. June 2019 · Paper 1 · Q19(c)(ii)
Mark scheme June 2019 Paper 1 Q19(c)(ii)
41. June 2019 · AS Paper 2 · Q4(b)(i)
Mark scheme June 2019 Paper 2 Q4(b)(i)
42. June 2019 · AS Paper 2 · Q4(b)(iii)
Mark scheme June 2019 Paper 2 Q4(b)(iii)
43. June 2019 · AS Paper 2 · Q4(c)
Mark scheme June 2019 Paper 2 Q4(c)
44. June 2019 · AS Paper 2 · Q4(d)
Mark scheme June 2019 Paper 2 Q4(d)
45. June 2019 · AS Paper 2 · Q4(e)(i)
Mark scheme June 2019 Paper 2 Q4(e)(i)
46. June 2019 · AS Paper 2 · Q4(e)(ii)
Mark scheme June 2019 Paper 2 Q4(e)(ii)
47. June 2018 · Paper 1 · Q14
Mark scheme June 2018 Paper 1 Q14
48. June 2018 · Paper 1 · Q20(b)
Mark scheme June 2018 Paper 1 Q20(b)
49. June 2018 · AS Paper 1 · Q23(b)
Mark scheme June 2018 Paper 1 Q23(b)
50. June 2018 · AS Paper 2 · Q4(c)
Mark scheme June 2018 Paper 2 Q4(c)
51. June 2018 · AS Paper 2 · Q5(b)
Mark scheme June 2018 Paper 2 Q5(b)
52. June 2018 · Paper 3 · Q2(a)(i)
Mark scheme June 2018 Paper 3 Q2(a)(i)
53. June 2017 · Paper 1 · Q19(b)
Mark scheme June 2017 Paper 1 Q19(b)
54. June 2017 · AS Paper 1 · Q23(a)
Mark scheme June 2017 Paper 1 Q23(a)
55. June 2017 · AS Paper 1 · Q23(b)
Mark scheme June 2017 Paper 1 Q23(b)
56. June 2017 · AS Paper 2 · Q2
Mark scheme June 2017 Paper 2 Q2
57. June 2016 · AS Paper 2 · Q5(a)(i)
Mark scheme June 2016 Paper 2 Q5(a)(i)
58. June 2016 · AS Paper 2 · Q5(b)(i)
Mark scheme June 2016 Paper 2 Q5(b)(i)
59. June 2016 · AS Paper 2 · Q5(b)(ii)
Mark scheme June 2016 Paper 2 Q5(b)(ii)
60. June 2016 · AS Paper 2 · Q5(c)
Mark scheme June 2016 Paper 2 Q5(c)