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Rates: orders, rate equations and the Arrhenius equation

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OCR AS and A-level Chemistry past-paper questions since 2016 · 46 parts · mark schemes follow the questions · www.chemistryaleveltutor.com · Questions and mark schemes © OCR

1. June 2025 · Paper 1 · Q9 · 1 marks ·
9 Hydrogen reacts with iodine monochloride, ICl , as shown in the equation: H2 + 2ICl 2HCl + I2 The mechanism for the reaction is: H2 + ICl HCl + HI slow step HI + ICl HCl + I2 fast step What is the rate equation for the reaction between H2 and ICl ? A rate = k [HI] [ICl ] B rate = k [H2] [ICl ] C rate = k [H2] [ICl ]2 D rate = k [H2] [HI] [ICl ]2 Your answer [1]
2. June 2025 · Paper 1 · Q12 · 1 marks ·
12 The rate constant, k, for a first order reaction is 6.19 × 10–3 s–1. What is the half-life, in s, for the reaction? A 4.29 × 10–3 B 49 C 112 D 323 Your answer [1]
3. June 2025 · Paper 1 · Q18(b) · 5 marks ·
(b) The following data was obtained in a series of experiments on the rate of the reaction for Reaction 18.1 at a constant temperature. Experiment [NO] / mol dm–3 [O2] / mol dm–3 rate / mol dm–3 s–1 1 0.040 0.035 7.45 × 10– 4 2 0.040 0.070 1.49 × 10–3 3 0.060 0.035 1.68 × 10–3 Determine the orders with respect to NO and O2. Explain your reasoning. Determine the rate equation and calculate the rate constant, k, including units. .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... k =......................... units ............................................................... [5]
4. June 2025 · Paper 1 · Q18(c)(i) · 1 marks ·
(c) The rate constant varies with temperature, according to the Arrhenius equation. A technician determines the activation energy for Reaction 18.1 by determining the rate constant, k, at different temperatures. The table shows the technician’s results. Temperature 1 T  / K–1 k ln k / K 1500 6.7 × 10–4 1.81 × 103 7.50 1750 5.7 × 10–4 8.51 × 104 .................... 2000 5.0 × 10–4 2.79 × 105 12.5 2250 4.4 × 10–4 1.47 × 106 14.2 2500 4.0 × 10– 4 5.70 × 106 15.6 (i) Complete the table by adding the missing value of ln k. [1]
5. June 2025 · Paper 1 · Q18(c)(ii) · 4 marks ·
(ii) Plot a graph of ln k against 1 T on the grid opposite. Use your graph to calculate the value of the activation energy, Ea, in kJ mol–1. Give your answer to 2 significant figures. Ea = ............................................ kJ mol–1 [4]
6. June 2025 · Paper 3 · Q3(b) · 6 marks ·
(b)* A reaction takes place when aqueous solutions of propanone, CH3COCH3(aq), and bromine, Br2(aq), are mixed in the presence of dilute acid, H+(aq). The overall equation for this reaction is shown below. CH3COCH3 + Br2 CH3COCH2Br + HBr Reaction 3.1 • A student carries out three experiments to investigate the rate of this reaction. • In each experiment, the student investigates the effect of changing the concentration of one of the three chemicals whilst keeping the concentrations of the other chemicals constant. The student’s results are shown below. Experiment 1 Only [CH3COCH3(aq)] is varied. Initial concentrations Initial rate CH3COCH3(aq) Br2(aq) H+(aq) / mol dm–3 s–1 / mol dm–3 / mol dm–3 / mol dm–3 1.50 × 10–3 2.00 × 10–1 2.50 × 10–1 1.70 × 10–7 4.50 × 10–3 2.00 × 10–1 2.50 × 10–1 5.10 × 10–7 Experiment 2 Only [Br2(aq)] is varied. [Br2(aq)] /mol dm–3 0 0 Time / s Experiment 3 Only [H+(aq)] varied. Initial rate /mol dm–3 s–1 0 0 [H+(aq)] /mol dm–3 Use the student’s results to determine the order with respect to each of the three chemicals, the rate equation and rate constant for Reaction 3.1. Explain your reasoning. Explain how the student’s results can be used to show that the mechanism of Reaction 3.1 has more than one step. .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... ..................................................................................................................................................... [6] Extra answer space if required. .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... ..........................................................................................................................................................
7. June 2024 · Paper 1 · Q9 · 1 marks ·
9 A graph of ln(k) is plotted against 1 / T for a reaction. (k = rate constant, T = temperature in K.) The gradient has the numerical value of –16 000. What is the activation energy, in kJ mol–1, for this reaction? A +1.92 B +133 C +1920 D +133 000 Your answer [1]
8. June 2024 · Paper 1 · Q10 · 1 marks ·
10 A reaction is zero order with respect to a reactant. Which rate–concentration graph for the reactant is the correct shape? A B C D Your answer [1]
9. June 2024 · Paper 1 · Q17(b) · 6 marks ·
(b)* Use the graph to determine the order of reaction with respect to CV, the rate of the reaction at three minutes and the rate constant, k. Your answer must show full working on the graph and on the lines below. [6] .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... Extra answer space if required. .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... ..........................................................................................................................................................
10. June 2024 · Paper 1 · Q20(b) · 2 marks ·
(b) Fluorine, F2, reacts with nitrogen dioxide, NO2, to form nitryl fluoride, NO2F, as shown in Reaction 20.1 below. F2 + 2NO2 2NO2F Reaction 20.1 The mechanism for this reaction involves two steps. Step 1 is the ‘slow’ step and Step 2 is the ‘fast’ step. The equation for Step 2 is shown below: F + NO2 NO2F Suggest the equation for Step 1 and the rate equation for Reaction 20.1. Equation for Step 1: ......................................................................................................................... Rate equation for Reaction 20.1: .................................................................................................... [2]
11. June 2023 · Paper 1 · Q7 · 1 marks · AO1
7 The reaction below is first order with respect to reactant X. X(aq) products When the initial concentration of X is 1.0 mol dm–3, the half-life is 16 minutes. What is the half-life when the initial concentration of X is 2.0 mol dm–3? A 2 minutes B 4 minutes C 8 minutes D 16 minutes Your answer [1]
12. June 2023 · Paper 1 · Q17 · 6 marks · AO3
17* Bromine, Br2, can be produced by the reaction: 5Br –(aq) + BrO3 –(aq) + 6H+(aq) 3Br2(aq) + 3H2O(l) A student investigates the rate of this reaction by carrying out four experiments at the same temperature. The student’s results are shown below. [Br – ] [BrO3 – ] [H+ ] Initial rate Experiment / mol dm–3 / mol dm–3 / mol dm–3 / mol dm–3 s–1 1 2.00 × 10–2 1.20 × 10–1 8.00 × 10–2 2.52 × 10–4 2 6.00 × 10–2 1.20 × 10–1 8.00 × 10–2 7.56 × 10–4 3 4.00 × 10–2 6.00 × 10–2 8.00 × 10–2 2.52 × 10–4 4 2.00 × 10–2 6.00 × 10–2 4.00 × 10–1 3.15 × 10–3 Explain how the reaction orders can be determined from the student’s results, and determine the rate equation and rate constant for this reaction. .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... ..................................................................................................................................................... [6] Additional answer space if required. .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... ..........................................................................................................................................................
13. June 2023 · Paper 3 · Q2(b) · 3 marks · AO3
(b) A student investigates the rate of a reaction that is 1st order with respect to hydrochloric acid, HCl (aq). • The student carries out a reaction using 0.680 mol dm–3 HCl (aq). The initial rate is 9.52 × 10–4 mol dm–3 s–1. • The student dilutes a different sample of 0.680 mol dm–3 HCl (aq) with water. The pH of this diluted acid is 1.50. • The student repeats the reaction using the same volume of this diluted acid. Determine the initial rate using this diluted acid. initial rate = ..................................... mol dm–3 s–1 [3]
14. June 2022 · Paper 1 · Q8 · 1 marks · AO1
8 The half-life for a first order reaction is 80 s. What is the rate constant k, in s–1, for this reaction? A 8.66 × 10–3 B 0.0125 C 55.5 D 115 Your answer [1]
15. June 2022 · Paper 1 · Q16(a)(ii) · 5 marks · AO1, 2, 3
(ii) The rate of Reaction 16.1 is investigated by carrying out three experiments at the same temperature. The results are shown below. [NO(g)] [CO(g)] Initial rate Experiment / mol dm–3 / mol dm–3 / mol dm–3 s–1 1 2.75 × 10–4 7.25 × 10–4 1.85 × 10–4 2 5.50 × 10–4 7.25 × 10–4 7.40 × 10–4 3 1.10 × 10–3 2.90 × 10–3 1.18 × 10–2 Determine the orders with respect to NO and CO, the rate equation, and the rate constant, k, including units. Explain your reasoning. ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... k = ............................................ units ....................... [5]
16. June 2022 · Paper 1 · Q16(b) · 2 marks · AO3
(b) Carbon monoxide also reacts with nitrogen dioxide as shown in Reaction 16.2. CO(g) + NO2(g) NO(g) + CO2(g) Reaction 16.2 The rate equation for Reaction 16.2 is shown below: rate = k [NO2(g)]2 Suggest a possible two-step mechanism for Reaction 16.2. The first step is much slower than the second step. step 1 ....................................................................................................................................... step 2 ....................................................................................................................................... [2]
17. 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]
18. November 2021 · Paper 1 · Q21(a)(i) · 2 marks · AO3
21 This question is about how the rate of reaction is affected by changes in conditions. A student carries out two investigations using the reaction between aqueous thiosulfate ions, S2O3 2–(aq), and aqueous hydrogen ions, H+(aq). Reaction 21.1 S2O3 2–(aq) + 2H+(aq) → S(s) + SO2(g) + H2O(l) (a) In Investigation 1, the student determines how the rate of Reaction 21.1 is affected by changes in concentration. The results are shown in the table. Experiment [S2O3 2–(aq)] [H+(aq)] initial rate / mol dm–3 / mol dm–3 / mol dm–3 s–1 1 0.16 1.00 0.0120 2 0.08 1.00 0.0060 3 0.02 0.50 0.0015 From the results, the student concludes that the rate equation is rate = k [S2O3 2–(aq)] (i) Explain how the student’s results support this rate equation. ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ...................................................................................................................................... [2]
19. November 2021 · Paper 1 · Q21(a)(ii) · 2 marks · AO3
(ii) Predict a possible two-step mechanism for Reaction 21.1. The first step is the rate-determining step. Step 1 ............................................................................................................................... Step 2 .......................................................................................................................... [2]
20. November 2021 · Paper 1 · Q21(b)(i) · 3 marks · AO2
(b) In Investigation 2 the student determines the rate constant k of Reaction 21.1 at different temperatures, T. From the results, the student plots a graph of ln k against 1 / T as shown below. 1 / T / 10–3 K–1 3.00 3.05 3.10 3.15 3.20 3.25 3.30 3.35 3.40 3.45 –1.50 –2.00 –2.50 In k –3.00 –3.50 – 4.00 – 4.50 Graph 21.2 (i) Calculate the activation energy, Ea, for Reaction 21.1, in kJ mol–1. Give your answer to 3 significant figures. Ea = ............................................ kJ mol–1 [3]
21. November 2021 · Paper 1 · Q21(b)(ii) · 1 marks · AO3
(ii) From the graph the student estimates the value of ln A as –2.00. (A is the pre-exponential factor.) Explain what mistake the student has made. ........................................................................................................................................... ........................................................................................................................................... ...................................................................................................................................... [1]
22. November 2021 · Paper 1 · Q21(b)(iii) · 2 marks · AO3
(iii) The student calculates the value of k in Investigation 1 as 0.075 s–1. Using Graph 21.2, determine the temperature, in °C, at which Investigation 1 was carried out. temperature = .................................................... °C [2]
23. November 2021 · Paper 3 · Q4(a) · 1 marks · AO3
4 Pent-1-ene and iodine react as shown in the equation below. CH3CH2CH2CH=CH2 + I2 CH3CH2CH2CHICH2I A student investigates the rate of this reaction by monitoring the concentration of iodine over time. The initial concentrations are shown in the table. Concentration / mol dm–3 I2 0.0200 CH3CH2CH2CH=CH2 2.0000 In this investigation, the order with respect to pent-1-ene can be assumed to be zero. The student plots the graph below from the experimental results. 0.0200 0.0150 [I2] 0.0100 / mol dm–3 0.0050 0.0000 0 1000 2000 3000 4000 5000 6000 7000 8000 time / s (a) Why can the order with respect to pent-1-ene be assumed to be zero in this investigation? ................................................................................................................................................... ................................................................................................................................................... .............................................................................................................................................. [1]
24. November 2021 · Paper 3 · Q4(b) · 6 marks · AO3
(b)* The student’s experimental procedure shows that the reaction is first order with respect to iodine. Show that this statement is true and determine the initial rate of reaction and rate constant. Assume that the reaction is zero order with respect to pent-1-ene. Show your working on the graph on page 10 and the lines below as appropriate. [6] ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... Additional answer space if required. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ...................................................................................................................................................
25. November 2021 · Paper 3 · Q4(c)(i) · 2 marks · AO2
(c) Further experiments provide evidence that the reaction is first order with respect to both CH3CH2CH2CH=CH2 AND I2. (i) Write equations to suggest a two-step mechanism for the reaction. Slow Fast [2]
26. November 2021 · Paper 3 · Q4(c)(ii) · 2 marks · AO3
(ii) Suggest how the investigation could be modified to show that the reaction is first order with respect to pent-1-ene. ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ...................................................................................................................................... [2]
27. November 2020 · Paper 1 · Q8 · 1 marks · AO2
8 A graph is plotted of ln(k) against 1 /T. (k = rate constant, T = temperature in K) The gradient has the numerical value of −55 000. What is the activation energy, in kJ mol−1? A +1.5 × 10−7 B +2.22 × 10−6 C +6.62 D +457 Your answer [1]
28. November 2020 · Paper 1 · Q10 · 1 marks · AO1
10 The equation for the reaction of ICl and H2 is shown below. 2ICl (g) + H2(g) 2HCl (g) + I2(g) The rate constant k for this reaction is 1.63 × 10−6 dm3 mol−1 s−1. What is the overall order of the reaction? A 0 B 1 C 2 D 3 Your answer [1]
29. November 2020 · Paper 1 · Q20(a)(i) · 1 marks · AO3
20 A student investigates the reaction between ethanoic acid, CH3COOH(l) and methanol, CH3OH(l), in the presence of an acid catalyst. The equation is shown below. CH3COOH(l) + CH3OH(l) CH3COOCH3(l) + H2O(l) (a) The student carries out an experiment to determine the order of reaction with respect to CH3COOH. The student uses a large excess of CH3OH. The temperature is kept constant throughout the experiment. The student takes a sample from the mixture every 20 minutes, and then determines the concentration of the ethanoic acid in each sample. From the experimental results, the student plots the graph below. 5.0 [CH3COOH] /10–3 mol dm–3 4.0 3.0 2.0 1.0 0 20 40 60 80 100 120 140 160 180 time / min (i) Explain why the student uses a large excess of methanol in this experiment. ........................................................................................................................................... ...................................................................................................................................... [1]
30. November 2020 · Paper 1 · Q20(a)(ii) · 2 marks · AO3
(ii) Use the half-life of this reaction to show that the reaction is first order with respect to CH3COOH. Show your working on the graph and below. ........................................................................................................................................... ...................................................................................................................................... [2]
31. November 2020 · Paper 1 · Q20(a)(iii) · 2 marks · AO3
(iii) Determine the initial rate of reaction. initial rate = ................................. mol dm−3 min−1 [2]
32. June 2019 · Paper 1 · Q11 · 1 marks · AO2
11 A graph of ln k against 1 T (T in K) for a reaction has a gradient with the numerical value of −4420. What is the activation energy, in kJ mol−1, for this reaction? A −532 B −36.7 C +36.7 D +5.32 × 105 Your answer [1]
33. June 2019 · Paper 1 · Q21 · 6 marks · AO3
21* Three students carry out a rates investigation on the reaction between bromine and propanone in the presence of hydrochloric acid. CH3COCH3(aq) + Br2(aq) CH3COCH2Br(aq) + HBr(aq) Each student investigates the effect of changing the concentration of one of the reactants whilst keeping the other concentrations constant. Their results are shown below. Results of student 1 [Br2(aq)] / mol dm–3 00 time /s Results of student 2 initial rate / mol dm–3s–1 00 [CH3COCH3(aq)] / mol dm–3 Results of student 3 [Br2(aq)] [CH3COCH3(aq)] [H+(aq)] Initial rate Experiment / mol dm−3 / mol dm−3 / mol dm−3 / 10−5 mol dm−3 s−1 1 0.004 1.60 0.20 1.25 2 0.004 1.60 0.40 2.50 Explain how the reaction orders can be determined from the students’ results, and determine the rate equation and rate constant. [6] .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... Additional answer space if required .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... ..........................................................................................................................................................
34. June 2019 · Paper 3 · Q1(e) · 1 marks · AO2
(e) A reaction is first order with respect to H+. At a pH of 1, the initial rate is 2.4 × 10−3 mol dm−3 s−1. What is the initial rate at a pH of 3? initial rate = ..................................... mol dm−3 s−1 [1]
35. June 2018 · Paper 1 · Q8 · 1 marks · AO1
8 A reaction is first order with respect to a reactant X. Which rate–concentration graph for reactant X is the correct shape? A B C D Your answer [1]
36. 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]
37. June 2018 · Paper 1 · Q17(a) · 6 marks ·
17 This question is about reaction rates. Aqueous iron(III) ions, Fe3+(aq), react with aqueous iodide ions, I–(aq), as shown below. 2Fe3+(aq) + 2I–(aq) 2Fe2+(aq) + I2(aq) A student carries out three experiments to investigate how different concentrations of Fe3+(aq) and I–(aq) affect the initial rate of this reaction. The results are shown below. [Fe3+(aq)] [I–(aq)] Initial rate Experiment / mol dm–3 / mol dm–3 / mol dm–3 s–1 1 4.00 × 10–2 3.00 × 10–2 8.10 × 10–4 2 8.00 × 10–2 3.00 × 10–2 1.62 × 10–3 3 4.00 × 10–2 6.00 × 10–2 3.24 × 10–3 (a)* Determine the rate constant and a possible two-step mechanism for this reaction that are consistent with these results. [6] ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... Additional answer space if required ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ...................................................................................................................................................
38. June 2018 · Paper 1 · Q17(b)(i) · 3 marks ·
(b) A student carries out an investigation to find the activation energy, Ea, and the pre-exponential factor, A, of a reaction. The student determines the rate constant, k, at different temperatures, T. The student then plots a graph of ln k against 1 / T as shown below. 33.00 32.00 31.00 30.00 In k 29.00 28.00 27.00 26.00 0.00 1.00 2.00 3.00 4.00 5.00 1 / T /10–3 K–1 (i) Draw a best-fit straight line and calculate the activation energy, in J mol–1. Give your answer to three significant figures. Show your working. activation energy, Ea = + ............................................. J mol–1 [3]
39. June 2018 · Paper 1 · Q17(b)(ii) · 2 marks ·
(ii) Use the graph to calculate the value of the pre-exponential factor, A. Show your working. pre-exponential factor, A = ......................................................... [2]
40. 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]
41. June 2018 · Paper 3 · Q6(a)(iii) · 3 marks ·
(iii) Reaction 6.1 takes place in two steps. OH– ions act as a catalyst. In step 1, ethanal reacts with OH– ions to set up an acid–base equilibrium. In step 2, compound A is formed. • Complete the equilibrium for step 1 and label the conjugate acid–base pairs as: A1, B1 and A2, B2. CH3CHO + OH– .......................... + .......................... ................. ................. ................. ................. • Suggest the equation for step 2. [3]
42. June 2017 · Paper 1 · Q10 · 1 marks ·
10 A reaction is zero order with respect to a reactant A. Which concentration–time graph for reactant A is the correct shape? A B C D Your answer [1]
43. 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]
44. June 2017 · Paper 1 · Q19(c) · 6 marks ·
(c)* Determine the initial rate of reaction, the order with respect to H2O2, and the rate constant. Your answer must show full working on the graph and on the lines below. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... .............................................................................................................................................. [6]
45. June 2017 · Paper 3 · Q3(a)(i) · 3 marks ·
3 This question is about reactions of hydrogen peroxide, H2O2. (a) Hydrogen peroxide, H2O2, iodide ions, I−, and acid, H+, react as shown in the equation below. H2O2(aq) + 2I−(aq) + 2H+(aq) I2(aq) + 2H2O(l) A student carries out several experiments at the same temperature, using the initial rates method, to determine the rate constant, k, for this reaction. The results are shown below. Initial concentrations Rate Experiment [H2O2(aq)] [I−(aq)] [H+(aq)] / 10−6 mol dm−3 s−1 / mol dm−3 / mol dm−3 / mol dm−3 1 0.0100 0.0100 0.100 2.00 2 0.0100 0.0200 0.100 4.00 3 0.0200 0.0100 0.100 4.00 4 0.0200 0.0100 0.200 4.00 (i) Determine the rate equation and calculate the rate constant, k, including units. k = ........................ units ........................ [3]
46. June 2017 · Paper 3 · Q3(a)(ii) · 3 marks ·
(ii) The rate constant, k, for this reaction is determined at different temperatures, T. Explain how the student could determine the activation energy, Ea, for the reaction graphically using values of k and T. ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ..................................................................................................................................... [3]

Mark schemes

1. June 2025 · Paper 1 · Q9
Mark scheme June 2025 Paper 1 Q9
2. June 2025 · Paper 1 · Q12
Mark scheme June 2025 Paper 1 Q12
3. June 2025 · Paper 1 · Q18(b)
Mark scheme June 2025 Paper 1 Q18(b)
4. June 2025 · Paper 1 · Q18(c)(i)
Mark scheme June 2025 Paper 1 Q18(c)(i)
5. June 2025 · Paper 1 · Q18(c)(ii)
Mark scheme June 2025 Paper 1 Q18(c)(ii)
6. June 2025 · Paper 3 · Q3(b)
Mark scheme June 2025 Paper 3 Q3(b)
7. June 2024 · Paper 1 · Q9
Mark scheme June 2024 Paper 1 Q9
8. June 2024 · Paper 1 · Q10
Mark scheme June 2024 Paper 1 Q10
9. June 2024 · Paper 1 · Q17(b)
Mark scheme June 2024 Paper 1 Q17(b)
10. June 2024 · Paper 1 · Q20(b)
Mark scheme June 2024 Paper 1 Q20(b)
11. June 2023 · Paper 1 · Q7
Mark scheme June 2023 Paper 1 Q7
12. June 2023 · Paper 1 · Q17
Mark scheme June 2023 Paper 1 Q17
13. June 2023 · Paper 3 · Q2(b)
Mark scheme June 2023 Paper 3 Q2(b)
14. June 2022 · Paper 1 · Q8
Mark scheme June 2022 Paper 1 Q8
15. June 2022 · Paper 1 · Q16(a)(ii)
Mark scheme June 2022 Paper 1 Q16(a)(ii)
16. June 2022 · Paper 1 · Q16(b)
Mark scheme June 2022 Paper 1 Q16(b)
17. June 2022 · Paper 3 · Q4(a)
Mark scheme June 2022 Paper 3 Q4(a)
18. November 2021 · Paper 1 · Q21(a)(i)
Mark scheme November 2021 Paper 1 Q21(a)(i)
19. November 2021 · Paper 1 · Q21(a)(ii)
Mark scheme November 2021 Paper 1 Q21(a)(ii)
20. November 2021 · Paper 1 · Q21(b)(i)
Mark scheme November 2021 Paper 1 Q21(b)(i)
21. November 2021 · Paper 1 · Q21(b)(ii)
Mark scheme November 2021 Paper 1 Q21(b)(ii)
22. November 2021 · Paper 1 · Q21(b)(iii)
Mark scheme November 2021 Paper 1 Q21(b)(iii)
23. November 2021 · Paper 3 · Q4(a)
Mark scheme November 2021 Paper 3 Q4(a)
24. November 2021 · Paper 3 · Q4(b)
Mark scheme November 2021 Paper 3 Q4(b)
25. November 2021 · Paper 3 · Q4(c)(i)
Mark scheme November 2021 Paper 3 Q4(c)(i)
26. November 2021 · Paper 3 · Q4(c)(ii)
Mark scheme November 2021 Paper 3 Q4(c)(ii)
27. November 2020 · Paper 1 · Q8
Mark scheme November 2020 Paper 1 Q8
28. November 2020 · Paper 1 · Q10
Mark scheme November 2020 Paper 1 Q10
29. November 2020 · Paper 1 · Q20(a)(i)
Mark scheme November 2020 Paper 1 Q20(a)(i)
30. November 2020 · Paper 1 · Q20(a)(ii)
Mark scheme November 2020 Paper 1 Q20(a)(ii)
31. November 2020 · Paper 1 · Q20(a)(iii)
Mark scheme November 2020 Paper 1 Q20(a)(iii)
32. June 2019 · Paper 1 · Q11
Mark scheme June 2019 Paper 1 Q11
33. June 2019 · Paper 1 · Q21
Mark scheme June 2019 Paper 1 Q21
34. June 2019 · Paper 3 · Q1(e)
Mark scheme June 2019 Paper 3 Q1(e)
35. June 2018 · Paper 1 · Q8
Mark scheme June 2018 Paper 1 Q8
36. June 2018 · Paper 1 · Q14
Mark scheme June 2018 Paper 1 Q14
37. June 2018 · Paper 1 · Q17(a)
Mark scheme June 2018 Paper 1 Q17(a)
38. June 2018 · Paper 1 · Q17(b)(i)
Mark scheme June 2018 Paper 1 Q17(b)(i)
39. June 2018 · Paper 1 · Q17(b)(ii)
Mark scheme June 2018 Paper 1 Q17(b)(ii)
40. June 2018 · Paper 3 · Q2(a)(i)
Mark scheme June 2018 Paper 3 Q2(a)(i)
41. June 2018 · Paper 3 · Q6(a)(iii)
Mark scheme June 2018 Paper 3 Q6(a)(iii)
42. June 2017 · Paper 1 · Q10
Mark scheme June 2017 Paper 1 Q10
43. June 2017 · Paper 1 · Q19(b)
Mark scheme June 2017 Paper 1 Q19(b)
44. June 2017 · Paper 1 · Q19(c)
Mark scheme June 2017 Paper 1 Q19(c)
45. June 2017 · Paper 3 · Q3(a)(i)
Mark scheme June 2017 Paper 3 Q3(a)(i)
46. June 2017 · Paper 3 · Q3(a)(ii)
Mark scheme June 2017 Paper 3 Q3(a)(ii)