plumiAlkanes: OCR A‑Level Chemistry A questions
Every OCR A-Level Chemistry A exam question on 4.1.2 Alkanes, 2016–2025, with its mark scheme and examiner’s report.
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Q16(d)
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Q4(a)
The whole paper ↗![June 2025 AS Paper 2, question 4(a): State and explain the trend in boiling points of the straight chain alkanes in Table 4.1. [4]](https://pub-e8a9dbab8e2a4d089f52b2a45e0d0b50.r2.dev/bank/h03202-jun25-04-a-qp.webp?v=3)
Q4(b)(i)
The whole paper ↗![June 2025 AS Paper 2, question 4(b)(i): Write the balanced equation for the complete combustion of one mole of pentane. [1]](https://pub-e8a9dbab8e2a4d089f52b2a45e0d0b50.r2.dev/bank/h03202-jun25-04-bi-qp.webp?v=3)
Q4(d)(i)
The whole paper ↗![June 2025 AS Paper 2, question 4(d)(i): Write an equation, using molecular formulae, for the formation of C3H7Br from propane. [1]](https://pub-e8a9dbab8e2a4d089f52b2a45e0d0b50.r2.dev/bank/h03202-jun25-04-di-qp.webp?v=3)
Q4(d)(iii)
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Q4(d)(iv)
The whole paper ↗![June 2025 AS Paper 2, question 4(d)(iv): Pentane C5H12 36 –3509 Hexane C6H14 69 –4163 (iv) Explain why two structural isomers of C3H7Br are formed. [1]](https://pub-e8a9dbab8e2a4d089f52b2a45e0d0b50.r2.dev/bank/h03202-jun25-04-div-qp.webp?v=3)
Q18(a)(i)
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Q18(a)(ii)
The whole paper ↗![June 2024 Paper 2, question 18(a)(ii): Describe two limitations of the synthesis of 2-bromo-2-methylpropane from an alkane and bromine. 1 2 [2]](https://pub-e8a9dbab8e2a4d089f52b2a45e0d0b50.r2.dev/bank/h43202-jun24-18-aii-qp.webp?v=3)
Q24(a)
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Q24(b)
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Q16(a)
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Q16(b)(i)
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Q16(b)(ii)
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Q23(a)(i)
The whole paper ↗![June 2023 AS Paper 1, question 23(a)(i): Heptane is one of the alkanes in petrol. Write the equation for the complete combustion of heptane. State symbols are not required. [2]](https://pub-e8a9dbab8e2a4d089f52b2a45e0d0b50.r2.dev/bank/h03201-jun23-23-ai-qp.webp?v=3)
Q25(a)
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Q25(b)
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Q5(b)(i)
The whole paper ↗![June 2022 Paper 3, question 5(b)(i): Write the equation for the complete combustion of this fuel. [1]](https://pub-e8a9dbab8e2a4d089f52b2a45e0d0b50.r2.dev/bank/h43203-jun22-05-bi-qp.webp?v=3)
Q5(a)(i)
The whole paper ↗![June 2022 AS Paper 2, question 5(a)(i): State the conditions for the formation of bromine radicals from bromine. [1]](https://pub-e8a9dbab8e2a4d089f52b2a45e0d0b50.r2.dev/bank/h03202-jun22-05-ai-qp.webp?v=3)
All 49 questions on Alkanes, as a list
- June 2025, Paper 2, Q16(d) (1 mark): Hexane, C6H14, is used as a fuel. 1.0 mol of hexane is mixed with 6.0 mol of oxygen and combusted. Construct an equation for the incomplete combustion of 1.0 mo
- June 2025, AS Paper 2, Q4(a) (4 marks): State and explain the trend in boiling points of the straight chain alkanes in Table 4.1. [4]
- June 2025, AS Paper 2, Q4(b)(i) (1 mark): Write the balanced equation for the complete combustion of one mole of pentane. [1]
- June 2025, AS Paper 2, Q4(d)(i) (1 mark): Write an equation, using molecular formulae, for the formation of C3H7Br from propane. [1]
- June 2025, AS Paper 2, Q4(d)(iii) (2 marks): Complete the equations for the propagation steps in the mechanism. Use molecular formulae for organic species and dots (•) for unpaired electrons on radicals. C
- June 2025, AS Paper 2, Q4(d)(iv) (1 mark): Pentane C5H12 36 –3509 Hexane C6H14 69 –4163 (iv) Explain why two structural isomers of C3H7Br are formed. [1]
- June 2024, Paper 2, Q18(a)(i) (3 marks): Write the equation for this reaction, showing the structures of the organic compounds. Name the reaction mechanism and the type of bond fission that occurs. Equ
- June 2024, Paper 2, Q18(a)(ii) (2 marks): Describe two limitations of the synthesis of 2-bromo-2-methylpropane from an alkane and bromine. 1 2 [2]
- June 2024, AS Paper 1, Q16 (1 mark): Which property explains the low reactivity of alkanes? A Low C–C bond enthalpy. B Low bond enthalpy of π‑bonds. C Low polarity of σ‑bonds. D Low reactivity of c
- June 2024, AS Paper 1, Q24(a) (4 marks): The skeletal formulae and boiling points of three isomers of C6H14 are shown in the table below. Molecular Boiling point / Isomer Skeletal formula formula °C A
- June 2024, AS Paper 1, Q24(b) (5 marks): The hydrocarbon C2H6 reacts with bromine, Br2, to form C2H5Br under suitable conditions. Complete the table below to show the mechanism for the three stages of
- June 2023, Paper 2, Q16(a) (4 marks): The boiling points of some hydrocarbons containing 6 carbon atoms are shown below. Hydrocarbon Boiling point / ºC 2,2-dimethylbutane 50 2-methylpentane 60 hexan
- June 2023, Paper 2, Q16(b)(i) (6 marks): Complete the table below to show the mechanism for the formation of 3-bromo-2-methylpentane and three possible equations for termination. In your equations, use
- June 2023, Paper 2, Q16(b)(ii) (2 marks): Organic compound A is formed by the substitution of all 14 H atoms in 2-methylpentane by Br atoms. Write the equation, using molecular formulae, for the formati
- June 2023, AS Paper 1, Q23(a)(i) (2 marks): Heptane is one of the alkanes in petrol. Write the equation for the complete combustion of heptane. State symbols are not required. [2]
- June 2023, AS Paper 1, Q25(a) (2 marks): The boiling points of 2 hydrocarbons are shown below. Hydrocarbon Boiling point / °C butane 0 pentane 36 Explain the difference in the boiling points of butane
- June 2023, AS Paper 1, Q25(b) (2 marks): Butane reacts with bromine by radical substitution to form a mixture of organic products. The reaction needs UV radiation for the initiation stage. Write equati
- June 2022, Paper 2, Q13 (1 mark): Which equation(s) could be part of the propagation step in the radical substitution of C5H12 to form C5H11Cl ? 1 C5H11• + Cl 2 C5H11Cl + Cl • 2 C5H12 + Cl • C5H
- June 2022, Paper 3, Q5(b)(i) (1 mark): Write the equation for the complete combustion of this fuel. [1]
- June 2022, AS Paper 2, Q5(a)(i) (1 mark): State the conditions for the formation of bromine radicals from bromine. [1]
- June 2022, AS Paper 2, Q5(a)(ii) (2 marks): Write two equations for the propagation steps in the mechanism for Reaction 5.1. Use structural formulae for organic species and dots (•) for unpaired electrons
- June 2022, AS Paper 2, Q5(a)(iii) (2 marks): The yield of CH3CH2CHBrCH3 is only 30%. Suggest two reasons why the yield of CH3CH2CHBrCH3 is so low. 1 2 [2]
- November 2021, Paper 2, Q1 (1 mark): 2-Methylbutane is reacted with chlorine by radical substitution. What is the number of structural isomers with the molecular formula C5H11Cl that could be forme
- November 2021, AS Paper 1, Q15 (1 mark): Which structural isomer of C7H16 has the weakest induced dipole–dipole interactions (London forces)? A 2,3-dimethylpentane B 3-ethylpentane C 2-methylhexane D 2
- November 2021, AS Paper 2, Q2(c) (2 marks): In this reaction with bromine, monosubstitution of alkane A forms a mixture of organic products. Show the structures of two monosubstituted organic products tha
- November 2021, AS Paper 2, Q2(d) (2 marks): With excess bromine, further substitution takes place. Write an equation for the reaction of alkane A with excess bromine to produce 1,3-dibromo-2-methylpropane
- November 2020, Paper 2, Q16(c) (3 marks): Complete the table to show the mechanism for the reaction of hydrocarbon A with Br2 to form (CH3)3CCHBrCH3. Use skeletal formulae for all organic compounds. Use
- November 2020, Paper 2, Q16(d) (2 marks): State two limitations of using radical substitution in organic synthesis. 1 2 [2]
- November 2020, AS Paper 1, Q15 (1 mark): Which property explains the low reactivity of alkanes? A Electron pair repulsion between σ-bonds B Free rotation about σ-bonds C High C–C bond enthalpy D High p
- June 2019, Paper 2, Q1 (1 mark): Which alkane has the highest boiling point? A CH3(CH2)5CH3 B (CH3)3CCH(CH3)2 C CH3(CH2)3CH(CH3)2 D (CH3)2CHCH2CH(CH3)2 Your answer [1]
- June 2019, Paper 2, Q2 (1 mark): Butane reacts with chlorine in the presence of ultraviolet radiation to form a mixture of organic products. Which equation shows a propagation step in the mecha
- June 2019, AS Paper 1, Q25(b)(i) (3 marks): Complete the table below to show the mechanism for the initiation and propagation stages of the reaction of C4H10 with chlorine to form C4H9Cl . In your equatio
- June 2019, AS Paper 1, Q25(b)(ii) (1 mark): Organic compound D is formed by substitution of all the H atoms in butane by Cl atoms. Write the equation for the formation of compound D from butane. Use molec
- June 2018, Paper 2, Q22(a) (1 mark): Write an equation for the incomplete combustion of heptane. [1]
- June 2018, Paper 2, Q22(b) (4 marks): Explain the difference in the boiling points of the fuels in Table 22.1. [4]
- June 2018, AS Paper 1, Q24(a) (5 marks): Compounds A, B and C are saturated hydrocarbons. The structures and boiling points of A, B and C are shown below. Isomer Boiling point / °C A 36 B 28 C 9 • Use
- June 2018, AS Paper 1, Q24(b)(i) (1 mark): Name the mechanism for this reaction. [1]
- June 2018, AS Paper 1, Q24(b)(ii) (2 marks): Complete the table to show the number of structural isomers of C5H11Cl that could be formed from the reaction of chlorine with A and B. A B Number of structural
- June 2018, AS Paper 1, Q24(b)(iii) (2 marks): The reaction of compound A with excess chlorine forms a compound D, which has a molar mass of 175.5 g mol−1. Draw a possible structure for compound D and write
- June 2017, Paper 2, Q14 (1 mark): Ethane reacts with chlorine by radical substitution to form chloroethane. Which radical(s) is/are present in the mechanism? 1 H 2 Cl 3 C2H5 A 1, 2 and 3 B On
- June 2017, Paper 2, Q16(a) (2 marks): Compound A and compound B are isomers. compound A compound B Compound A has a lower melting point than compound B. Suggest why. [2]
- June 2017, Paper 3, Q1(e) (1 mark): Suggest why some industries are interested in the presence of ‘methane hydrate’ in regions of the Earth. [1]
- June 2017, AS Paper 1, Q17 (1 mark): Which organic compound has the lowest boiling point? A 2,3,4-trimethylpentane B 2,3-dimethylhexane C 2-methylheptane D octane Your answer [1]
- June 2017, AS Paper 2, Q5(d)(i) (1 mark): State the conditions for the reaction. [1]
- June 2017, AS Paper 2, Q5(d)(ii) (1 mark): Write the overall equation for the reaction. [1]
- June 2017, AS Paper 2, Q5(d)(iv) (2 marks): Write two equations to show the propagation steps in the mechanism for this reaction. Use dots,•, to show the unpaired electrons on radicals. [2]
- June 2017, AS Paper 2, Q5(d)(v) (1 mark): Draw the displayed formula of the radical formed in the first propagation step. Use a dot,•, to show the position of the unpaired electron. [1]
- June 2017, AS Paper 2, Q5(d)(vi) (1 mark): Further substitution forms a mixture of organic products. Draw the structure of an organic product formed from 2-chloropropanoic acid by further substitution. [
- June 2016, AS Paper 1, Q17 (1 mark): Chlorine reacts with 1-chloropropane in the presence of ultraviolet radiation via a radical substitution mechanism. Which equation shows a propagation step in t
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