plumiConcentration–time graphs and half-life: OCR A‑Level Chemistry A questions
OCR A-Level Chemistry A past-paper questions on 5.1.1.2 Concentration–time graphs and half-life, 2016–2025, with mark schemes and examiner’s reports where available.
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Open the full PDFYour answerQ3(b)
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Open the full PDFYour answerQ4(b)
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All 11 questions on Concentration–time graphs and half-life, as a list
- 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 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, 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 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 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
- 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 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, 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 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(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
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