plumiHow fast?: OCR A‑Level Chemistry A questions
Every OCR A-Level Chemistry A exam question on 5.1.1 How fast?, 2016–2025, with its mark scheme and examiner’s report.
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Q18(b)
The whole paper ↗![June 2025 Paper 1, question 18(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. [NO] / mol dm–3 [O2] / mol d](https://pub-e8a9dbab8e2a4d089f52b2a45e0d0b50.r2.dev/bank/h43201-jun25-18-b-qp.webp?v=3)
Q18(c)(i)
The whole paper ↗![June 2025 Paper 1, question 18(c)(i): Complete the table by adding the missing value of ln k. [1]](https://pub-e8a9dbab8e2a4d089f52b2a45e0d0b50.r2.dev/bank/h43201-jun25-18-ci-qp.webp?v=3)
Q18(c)(ii)
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Q3(b)
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![June 2024 Paper 1, question 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]](https://pub-e8a9dbab8e2a4d089f52b2a45e0d0b50.r2.dev/bank/h43201-jun24-10-qp.webp?v=3)
Q17(b)
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Q20(b)
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Q2(b)
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![June 2022 Paper 1, question 8: The half-life for a first order reaction is 80 s. What is the rate constant k, in s–1, for this reaction? 8.66 × 10–3 A B 0.0125 C 55.5 D 115 [1] Your answer](https://pub-e8a9dbab8e2a4d089f52b2a45e0d0b50.r2.dev/bank/h43201-jun22-08-qp.webp?v=3)
Q16(a)(ii)
The whole paper ↗![June 2022 Paper 1, question 16(a)(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 E](https://pub-e8a9dbab8e2a4d089f52b2a45e0d0b50.r2.dev/bank/h43201-jun22-16-aii-qp.webp?v=3)
Q16(b)
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Q21(a)(i)
The whole paper ↗![November 2021 Paper 1, question 21(a)(i): Explain how the student’s results support this rate equation. [2]](https://pub-e8a9dbab8e2a4d089f52b2a45e0d0b50.r2.dev/bank/h43201-nov21-21-ai-qp.webp?v=3)
Q21(a)(ii)
The whole paper ↗![November 2021 Paper 1, question 21(a)(ii): Predict a possible two-step mechanism for Reaction 21.1. The first step is the rate-determining step. Step 1 Step 2 [2]](https://pub-e8a9dbab8e2a4d089f52b2a45e0d0b50.r2.dev/bank/h43201-nov21-21-aii-qp.webp?v=3)
Q21(b)(i)
The whole paper ↗![November 2021 Paper 1, question 21(b)(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]](https://pub-e8a9dbab8e2a4d089f52b2a45e0d0b50.r2.dev/bank/h43201-nov21-21-bi-qp.webp?v=3)
Q21(b)(ii)
The whole paper ↗![November 2021 Paper 1, question 21(b)(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]](https://pub-e8a9dbab8e2a4d089f52b2a45e0d0b50.r2.dev/bank/h43201-nov21-21-bii-qp.webp?v=3)
All 42 questions on How fast?, as a list
- June 2025, Paper 1, Q9 (1 mark): 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
- June 2025, Paper 1, Q12 (1 mark): 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? 4.29 × 10–3 A B 49 C 112 D 323 Your answer [
- June 2025, Paper 1, Q18(b) (5 marks): The following data was obtained in a series of experiments on the rate of the reaction for Reaction 18.1 at a constant temperature. [NO] / mol dm–3 [O2] / mol d
- June 2025, Paper 1, Q18(c)(i) (1 mark): Complete the table by adding the missing value of ln k. [1]
- June 2025, Paper 1, Q18(c)(ii) (4 marks): 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 si
- June 2025, Paper 3, Q3(b) (6 marks): This question is about equilibrium and rates. (b)* A reaction takes place when aqueous solutions of propanone, CH3COCH3(aq), and bromine, Br2(aq), are mixed in
- June 2024, Paper 1, Q9 (1 mark): 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 th
- June 2024, Paper 1, Q10 (1 mark): 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]
- June 2024, Paper 1, Q17(b) (6 marks): 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
- June 2024, Paper 1, Q20(b) (2 marks): 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
- June 2023, Paper 1, Q7 (1 mark): 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. W
- June 2023, Paper 1, Q17 (6 marks): 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 carry
- June 2023, Paper 3, Q2(b) (3 marks): 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
- June 2022, Paper 1, Q8 (1 mark): The half-life for a first order reaction is 80 s. What is the rate constant k, in s–1, for this reaction? 8.66 × 10–3 A B 0.0125 C 55.5 D 115 [1] Your answer
- June 2022, Paper 1, Q16(a)(ii) (5 marks): 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 E
- June 2022, Paper 1, Q16(b) (2 marks): 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
- November 2021, Paper 1, Q21(a)(i) (2 marks): Explain how the student’s results support this rate equation. [2]
- November 2021, Paper 1, Q21(a)(ii) (2 marks): Predict a possible two-step mechanism for Reaction 21.1. The first step is the rate-determining step. Step 1 Step 2 [2]
- November 2021, Paper 1, Q21(b)(i) (3 marks): 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]
- November 2021, Paper 1, Q21(b)(ii) (1 mark): 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]
- November 2021, Paper 1, Q21(b)(iii) (2 marks): 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
- November 2021, Paper 3, Q4(a) (1 mark): Why can the order with respect to pent-1-ene be assumed to be zero in this investigation? [1]
- November 2021, Paper 3, Q4(b) (6 marks): 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
- November 2021, Paper 3, Q4(c)(i) (2 marks): Write equations to suggest a two-step mechanism for the reaction. Slow Fast [2]
- November 2021, Paper 3, Q4(c)(ii) (2 marks): Suggest how the investigation could be modified to show that the reaction is first order with respect to pent-1-ene. [2]
- November 2020, Paper 1, Q8 (1 mark): 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 ener
- November 2020, Paper 1, Q10 (1 mark): 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
- November 2020, Paper 1, Q20(a)(i) (1 mark): Explain why the student uses a large excess of methanol in this experiment. [1]
- November 2020, Paper 1, Q20(a)(ii) (2 marks): 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]
- November 2020, Paper 1, Q20(a)(iii) (2 marks): Determine the initial rate of reaction. initial rate = mol dm−3 min−1 [2]
- June 2019, Paper 1, Q11 (1 mark): 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 react
- June 2019, Paper 1, Q21 (6 marks): 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) CH
- June 2019, Paper 3, Q1(e) (1 mark): 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?
- June 2018, Paper 1, Q8 (1 mark): 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 [1] Your answer
- June 2018, Paper 1, Q17(a) (6 marks): 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) +
- June 2018, Paper 1, Q17(b)(i) (3 marks): 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 ener
- June 2018, Paper 1, Q17(b)(ii) (2 marks): Use the graph to calculate the value of the pre-exponential factor, A. Show your working. pre-exponential factor, A = [2]
- June 2017, Paper 1, Q10 (1 mark): 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 [1] Your answer
- June 2017, Paper 1, Q19(b) (1 mark): Suggest a different experimental method that would allow the rate of this reaction to be followed over time. [1]
- June 2017, Paper 1, Q19(c) (6 marks): Aqueous solutions of hydrogen peroxide, H2O2(aq), decompose as in the equation below. 2H2O2(aq) 2H2O(l) + O2(g) A student investigates the decomposition of H2O2
- June 2017, Paper 3, Q3(a)(i) (3 marks): Determine the rate equation and calculate the rate constant, k, including units. k = units [3]
- June 2017, Paper 3, Q3(a)(ii) (3 marks): 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 r
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