Alkanes: Edexcel International A Level Chemistry questions

Every Edexcel International A Level Chemistry exam question on 4B Alkanes (specification points 4.9–4.18), 2019–2025, with its mark scheme and examiner’s report.

All 125 questions on Alkanes, as a list

June 2025, AS Unit 1, Q13 (1 mark): Which type of reaction occurs when an alkane is cracked? A combustion B hydrolysis C neutralisation D thermal decomposition
June 2025, AS Unit 1, Q15 (1 mark): One molecule of a hydrocarbon is cracked to form two molecules of ethene, two molecules of propene and one molecule of propane. What is the molecular formula of
June 2025, AS Unit 1, Q17 (1 mark): Which structures represent a pair of isomers? A B C D
June 2025, AS Unit 1, Q20(b)(i) (1 mark): State what is meant by complete combustion. (1)
June 2025, AS Unit 1, Q20(b)(ii) (2 marks): Write a balanced equation for the complete combustion of dodecane, C12H26 . Include state symbols. (2)
June 2025, AS Unit 1, Q20(b)(iv) (2 marks): The formula C12H26 represents many isomers, including six diethyloctanes. The names of four of these diethyloctanes are 3,3-diethyloctane, 3,4-diethyloctane, 3,
June 2025, AS Unit 1, Q22(a) (1 mark): Name the type and mechanism for the reaction between halogens and alkanes. (1)
June 2025, AS Unit 1, Q22(b)(i) (2 marks): Give the equation for the initiation step. Include appropriate arrows and electrons. (2)
June 2025, AS Unit 1, Q22(b)(ii) (2 marks): Give an equation for each of the first two propagation steps. (2) First propagation step Second propagation step
June 2025, AS Unit 1, Q22(b)(iii) (1 mark): Give the equation for the termination step to form an alkane. (1)
June 2025, AS Unit 2, Q14(b)(ii) (3 marks): Hydrogen has been proposed as an alternative fuel to petrol. Explain why hydrogen is a more environmentally friendly fuel than alkanes. (3)
January 2025, AS Unit 1, Q15 (1 mark): What is the IUPAC name for the hydrocarbon shown? A 2‑ethyl‑3‑methylnonane B 3,4‑dimethyldecane C 8‑ethyl‑7‑methylnonane D 7,8‑dimethyldecane
January 2025, AS Unit 1, Q16 (1 mark): Which statement about the cracking of crude oil is true? The cracking of crude oil A separates the mixture into pure compounds B separates the mixture into frac
January 2025, AS Unit 1, Q18 (1 mark): Which of these formulae are correct for the compound 1,4‑diethylcyclohexene? C10H18 C5H9 (i) (ii) (iii) skeletal formula molecular formula empirical formula A n
January 2025, AS Unit 1, Q24(c) (2 marks): Identify, by name or formula, two possible structural isomers of X using your answers to (a)(iv) and (b). (2)
January 2025, AS Unit 1, Q25(a)(i) (1 mark): Name the mechanism and type of this reaction. (1)
January 2025, AS Unit 1, Q25(a)(ii) (1 mark): Give the essential condition for Step 1 to occur. (1)
January 2025, AS Unit 1, Q25(a)(iii) (1 mark): Name the type of step illustrated by Step 3. (1)
January 2025, AS Unit 1, Q25(a)(iv) (4 marks): A different type of step, other than the ones shown, also occurs in the reaction. Describe this type of step, including two possible examples which might occur
October 2024, AS Unit 1, Q13 (1 mark): Cycloalkanes undergo free radical substitution reactions by the same mechanism as methane. Three isomeric cycloalkanes are shown. Isomer X Isomer Y Isomer Z Whi
October 2024, AS Unit 1, Q18(a) (3 marks): Give the molecular formula, empirical formula and IUPAC name for isooctane. (3) Molecular formula Empirical formula . IUPAC name .
October 2024, AS Unit 1, Q18(b)(i) (1 mark): Name the technique that could be used for this separation. (1)
October 2024, AS Unit 1, Q18(b)(ii) (2 marks): Describe how this technique separates isooctane from octane. (2)
October 2024, AS Unit 1, Q18(c)(i) (1 mark): Write the equation for the complete combustion of isooctane. State symbols are not required. (1)
October 2024, AS Unit 1, Q18(c)(ii) (4 marks): Carbon monoxide and nitrogen monoxide are both pollutants produced in car engines. Describe how each pollutant is formed in car engines, including the condition
October 2024, AS Unit 1, Q18(c)(iii) (1 mark): Identify another pollutant, other than carbon dioxide, carbon monoxide and nitrogen monoxide, produced in car engines. (1)
October 2024, AS Unit 1, Q18(d)(i) (1 mark): State the type and mechanism of this reaction. (1)
October 2024, AS Unit 1, Q18(d)(ii) (1 mark): Give the essential condition required. (1)
October 2024, AS Unit 2, Q11 (1 mark): Which alkane has the highest boiling temperature? A hexane B pentane C 2-methylpentane D 2,3-dimethylbutane
June 2024, AS Unit 1, Q4 (1 mark): What is the best definition of a hydrocarbon? A a compound containing carbon, hydrogen and oxygen B a compound containing carbon and hydrogen only C a compound
January 2024, AS Unit 1, Q14 (1 mark): How many structural isomers have the formula C6H14? A 3 B 4 C 5 D 6 Use this space for any rough working. Anything you write in this space will gain no credit.
January 2024, AS Unit 1, Q16 (1 mark): Which mixture could be formed when a single molecule of C12H26 is cracked? A butene, pentane and propene B hexane, butene and ethane C nonane and ethene D prope
January 2024, AS Unit 1, Q17 (1 mark): The substances formed from the combustion of petrol in car engines include A water, carbon dioxide and hydrogen B water, carbon monoxide and hydrogen chloride C
January 2024, AS Unit 1, Q19(b)(i) (2 marks): Show the initiation step of this reaction. Include appropriate arrows and the conditions necessary for this step. (2)
January 2024, AS Unit 1, Q19(b)(ii) (2 marks): Using your answer to (b)(i), state what is meant by the terms homolytic and free radical. (2) homolytic free radical
January 2024, AS Unit 1, Q19(b)(iii) (1 mark): Suggest why this method has limited use in the synthesis of organic compounds. (1)
January 2024, AS Unit 1, Q22(b) (1 mark): The unknown gas is a hydrocarbon. Give the name or formula for the unknown gas using your answer to (a). (1)
October 2023, AS Unit 1, Q15 (1 mark): What is the number of structural isomers with the molecular formula C5H12? A six B five C four D three
October 2023, AS Unit 1, Q19(b) (3 marks): Many countries are gradually replacing E5 fuels with E10 fuels. Explain how this change might result in a more sustainable fuel. (3)
October 2023, AS Unit 1, Q19(c)(i) (1 mark): Write the equation for this reaction using molecular formulae. State symbols are not required. (1)
October 2023, AS Unit 1, Q19(c)(ii) (1 mark): Draw the structure of the cyclic hydrocarbon formed in this reaction. (1)
October 2023, AS Unit 1, Q19(d)(i) (2 marks): Describe the role of the ultraviolet light in the initiation step of this reaction. (2)
October 2023, AS Unit 1, Q19(d)(ii) (2 marks): The alkane dodecane, C12H26, is formed in this reaction. Write equations for the propagation step and for the termination step for the formation of this product
January 2023, AS Unit 1, Q16 (1 mark): Which is the skeletal structure for 3,4‑dichloro‑2,2‑dimethylpentane? Cl A Cl Cl Cl B C Cl Cl Cl Cl D
January 2023, AS Unit 1, Q18 (1 mark): Which is not a step in the reaction of chlorine with propane in ultraviolet radiation? A C3H7· + Cl· → C3H7Cl B C3H7· + C3H7· → C6H14 C C3H7· + Cl2 → C3H7Cl + C
January 2023, AS Unit 1, Q19 (1 mark): Why does free radical substitution have limited use in industrial chemistry? A the reactions only occur in the upper atmosphere B initiation requires ultraviole
January 2023, AS Unit 1, Q21(a)(i) (2 marks): Give the molecular formula and IUPAC name for X. (2)
January 2023, AS Unit 1, Q21(a)(ii) (1 mark): Name the industrial process used to produce X from the straight‑chain isomer. (1)
January 2023, AS Unit 1, Q21(b)(i) (2 marks): Write an equation for the complete combustion of heptane. Include state symbols. (2)
January 2023, AS Unit 1, Q21(b)(ii) (1 mark): Identify, by name or formula, a pollutant that may result from the incomplete combustion of heptane. (1)
January 2023, AS Unit 1, Q21(c) (2 marks): Recently, sales of electric cars have increased. Give two environmental benefits of using electric cars. Justify your answers. (2)
January 2023, AS Unit 1, Q23(a) (1 mark): Suggest one difference between the fractional distillation of air and of crude oil. (1)
October 2022, AS Unit 1, Q6(a) (1 mark): What is the most significant hazard associated with the pollutant CO(g)? (1) A it is a major contributor to the formation of acid rain B it strongly absorbs inf
October 2022, AS Unit 1, Q7(a) (1 mark): What is the role of ultraviolet radiation in the reaction? (1) A to break the Br Br bond only B to break a C H bond only C to break a C C bond only D to break b
October 2022, AS Unit 1, Q7(b) (1 mark): One of the steps of the reaction is shown. C8H17• + Br2 → C8H17Br + Br• What is the name of this step and the type of bond breaking that takes place in the brom
October 2022, AS Unit 1, Q7(c) (1 mark): What is the overall equation for the reaction of octane with bromine? (1) A C8H18 + Br2 → C8H16Br2 + H2 B C8H18 + Br2 → C8H17Br + HBr C C8H18 + Br2 → 2C4H9Br D
October 2022, AS Unit 1, Q15(a)(i) (1 mark): Give the IUPAC name for iso‑octane. (1)
October 2022, AS Unit 1, Q15(a)(ii) (1 mark): Name the industrial process used to convert octane into iso‑octane. (1)
October 2022, AS Unit 1, Q15(a)(iii) (1 mark): Give a reason why petrol needs a high proportion of iso‑octane. (1)
October 2022, AS Unit 2, Q6 (1 mark): How many structural isomers with the molecular formula C5H10O react with Benedict’s or Fehling’s solutions? A 2 B 3 C 4 D 5
June 2022, AS Unit 1, Q16 (1 mark): Which of these atmospheric pollutants is not emitted during the combustion of alkane car fuels? A ammonia B nitrogen dioxide C sulfur dioxide D octane
June 2022, AS Unit 1, Q17 (1 mark): Which of these occurs in a propagation step in the reaction of methane with chlorine? A H3C Cl B H3C Cl Cl C H3C H CH3 D Cl Cl H3C H
June 2022, AS Unit 1, Q22(a) (1 mark): On the structure of zingiberene, draw a circle around the ‘2‑methyl’ group referred to in the IUPAC name. (1) zingiberene
June 2022, AS Unit 1, Q23(a)(ii) (2 marks): State the main environmental problem caused by landfill gases, identifying the gas or gases responsible. (2)
June 2022, AS Unit 2, Q18(a)(ii) (2 marks): Write the equation for the complete combustion of 2,2,4-trimethylpentane, using molecular formulae. State symbols are not required. (2)
January 2022, AS Unit 1, Q10(a) (1 mark): What is the equation for the reaction? (1) A C2H6 + Br2 ® C2H4Br2 + H2 B C2H6 + Br2 ® C2H5Br + HBr C C2H6 + Br2 ® 2CH3Br D C2H6 + Br2 ® CH4 + CH2Br2
January 2022, AS Unit 1, Q10(b) (1 mark): The ultraviolet radiation is needed for (1) A homolytic breaking of a Br–Br bond B heterolytic breaking of a Br–Br bond C homolytic breaking of a C–H bond D het
January 2022, AS Unit 1, Q11 (1 mark): All alkanes have the same A empirical formula B general formula C molecular formula D structural formula
January 2022, AS Unit 1, Q12 (1 mark): A single molecule of decane, C10H22 , is cracked. Which of these mixtures could not be formed? A pentene and pentane B ethene, butene and butane C propene, prop
January 2022, AS Unit 1, Q13 (1 mark): How many structural isomers have the formula C3H6Cl2? A 2 B 3 C 4 D 5
January 2022, AS Unit 1, Q15 (1 mark): Which pollutant cannot form when alkane fuels are burned in car engines? A hydrogen chloride B sulfur dioxide C carbon particulates D carbon monoxide Use this s
January 2022, AS Unit 1, Q24(b) (1 mark): The organic liquid C is a hydrocarbon. Give a possible name or formula for C, using your answer in (a). (1)
January 2022, AS Unit 2, Q24(c) (1 mark): State why NOx emissions are harmful to the environment. (1)
October 2021, AS Unit 1, Q10(a) (1 mark): Which process occurs in the initiation step? (1) A Cl Cl B Cl Cl C Cl Cl D Cl Cl
October 2021, AS Unit 1, Q10(b) (1 mark): Which of these molecules could not be formed in a termination step? (1) A C2H6 B CH3Cl C CH2Cl2 D HCl Use this space for any rough working. Anything you write i
October 2021, AS Unit 1, Q14(d)(ii) (2 marks): Give two possible reasons for producing hydrogen from aluminium rather than from fossil fuels. (2)
October 2021, AS Unit 1, Q15(a) (2 marks): Describe how a sample of octadecane can be obtained from a mixture of alkanes. (2)
October 2021, AS Unit 1, Q15(b)(i) (1 mark): Octadecane can be cracked to produce butene and one other product. Complete the equation. State symbols are not required. C18H38 → 2C4H8 + (1)
October 2021, AS Unit 1, Q15(b)(ii) (2 marks): One of the products of this cracking reaction is but-1-ene. Give the skeletal formulae for the other three alkene isomers of C4H8 (2)
October 2021, AS Unit 1, Q15(e)(ii) (2 marks): Explain the main hazard when using butane as a fuel in a portable heater in an enclosed space. (2)
June 2021, AS Unit 1, Q13 (1 mark): When C20H42 is cracked, each molecule produces one molecule of ethene, one molecule of butane and two molecules of hydrocarbon E. What is the molecular formula
June 2021, AS Unit 1, Q21(a)(i) (1 mark): Give a reason why incomplete combustion sometimes occurs. (1)
June 2021, AS Unit 1, Q21(a)(ii) (1 mark): Write the equation for the incomplete combustion of heptane, forming carbon monoxide and water as the only products. State symbols are not required. (1)
June 2021, AS Unit 1, Q21(b)(i) (2 marks): Draw the skeletal formulae of a branched-chain alkane and a cycloalkane, each containing seven carbon atoms. (2) Branched-chain alkane Cycloalkane
June 2021, AS Unit 1, Q21(b)(ii) (1 mark): Write the equation for the reforming of heptane into a cycloalkane. Use molecular formulae. (1)
June 2021, AS Unit 1, Q21(b)(iii) (1 mark): Give a reason for adding cycloalkanes to petrol. (1) .
June 2021, AS Unit 1, Q21(c)(i) (2 marks): State the type and mechanism of this reaction. (2)
June 2021, AS Unit 1, Q21(c)(ii) (7 marks): Give the mechanism for the reaction to produce C7H15Cl, C14H30 and HCl as the only products. Include the name of each of the steps in your mechanism. Curly half
January 2021, AS Unit 1, Q14 (1 mark): What is the IUPAC name of this alkane? A 2-ethyl-4,5-dimethylheptane B 6-ethyl-3,4-dimethylheptane C 3,4,6-trimethyloctane D 3,5,6-trimethyloctane
January 2021, AS Unit 1, Q15 (1 mark): Petrol, bioethanol and hydrogen are fuels. All three of these fuels A burn to produce greenhouse gases B are overall carbon neutral C are overall sustainable D
January 2021, AS Unit 1, Q16(a) (1 mark): Which of these is an overall equation for this reaction? (1) A C5H8 + Br2 → C5H8Br2 B C5H10 + Br2 → C5H10Br2 C C5H10 + Br2 → C5H8Br2 + H2 D C5H10 + Br2 → C5H9Br
January 2021, AS Unit 1, Q16(b) (1 mark): Which statement is not correct about this reaction system? (1) A only the initiation step involves homolytic bond fission B only some bromine is converted to fr
January 2021, AS Unit 1, Q16(c) (1 mark): Which free radical is least likely to form in a propagation step in this reaction system? (1) A C5H9• B Br• C C5H8Br• D H•
January 2021, AS Unit 1, Q16(d) (1 mark): Which alkane could be formed in a termination step in this reaction system? (1) A B C D Use this space for any rough working. Anything you write in this space w
January 2021, AS Unit 1, Q20(a) (2 marks): Write an equation for the incomplete combustion of one mole of propene to form carbon dioxide, carbon monoxide, carbon and water as the only products. Include s
January 2021, AS Unit 1, Q21(a) (2 marks): Suggest two properties that make squalane useful in cosmetics. (2)
January 2021, AS Unit 1, Q21(b) (1 mark): Give the molecular formula of squalane. (1)
January 2021, AS Unit 1, Q21(d)(i) (1 mark): Suggest the name of a suitable technique to obtain squalene from shark liver oil. (1)
January 2021, AS Unit 1, Q21(f)(i) (2 marks): State what is meant by the term structural isomers. (2)
January 2021, AS Unit 1, Q21(f)(iii) (1 mark): Complete the diagram to show another structural isomer of C15H24 . (1)
January 2021, Unit 5, Q22(b) (2 marks): When CxHy was added to a little bromine water and the mixture shaken, the bromine water remained yellow. Suggest two possible structures for CxHy . (2)
October 2020, AS Unit 2, Q17(c)(i) (2 marks): Methanol produced from petrol by CCU may be mixed with petrol derived from fossil fuels. A concentration of 5% by mass of methanol is used. Explain how the use
October 2020, Unit 5, Q4 (1 mark): Chlorine reacts with methylbenzene in the presence of ultraviolet light. Which of these is a product of this reaction? CH2Cl Cl A B Cl CH3 CH2Cl C D Cl Cl Cl Us
January 2020, AS Unit 1, Q14 (1 mark): Some equations for reactions used in reforming crude oil fractions are shown. Which equation is not balanced? A o B o + H2 C o + 3H2 D o + 3H2
January 2020, AS Unit 1, Q15 (1 mark): A pure alkane fuel is burned in air. Which substance is not a possible combustion product? A H2 B H2O C CO D CO2 Use this space for any rough working. Anything
January 2020, AS Unit 1, Q20(a) (4 marks): The skeletal formula of hexane is Draw the four structural isomers of hexane in the boxes. (4) Isomer 1 Isomer 2 Isomer 3 Isomer 4
January 2020, AS Unit 1, Q20(b)(i) (2 marks): Draw the initiation step of this reaction, using curly half-arrows. (2)
January 2020, AS Unit 1, Q20(b)(ii) (2 marks): Write equations for two propagation steps to show how C6H13Br is formed. Curly arrows are not required. (2)
January 2020, AS Unit 1, Q20(b)(iii) (1 mark): Give the molecular formula of an alkane formed in a termination step in this reaction. (1)
January 2020, AS Unit 1, Q20(b)(iv) (3 marks): Calculate the percentage by mass of bromine in the heaviest molecule containing six carbon atoms that could form when hexane reacts with a large excess of bromi
January 2020, AS Unit 2, Q18(d)(iv) (2 marks): Give two reasons why it is important to remove nitrogen oxides from the exhaust gases of diesel engines. (2)
June 2019, AS Unit 1, Q22(a)(i) (2 marks): Explain why coffee grounds might be considered a carbon-neutral fuel. (2)
June 2019, AS Unit 1, Q22(a)(ii) (2 marks): Explain how the use of fossil fuels causes climate change. (2)
June 2019, AS Unit 1, Q22(b)(i) (1 mark): Name another pollutant formed by incomplete combustion of alkanes. (1)
June 2019, AS Unit 1, Q22(b)(ii) (2 marks): Write the equation for the complete combustion of octane. State symbols are not required. (2)
June 2019, AS Unit 1, Q22(c)(i) (1 mark): Name this process. (1)
January 2019, AS Unit 1, Q13 (1 mark): An electrophile A accepts a pair of electrons B always has a negative charge C always has a positive charge D donates a pair of electrons
January 2019, AS Unit 1, Q21(a)(i) (1 mark): Give a reason why petrol should not contain a high proportion of heptane. (1)
January 2019, AS Unit 1, Q21(a)(ii) (1 mark): Draw the skeletal formula of 2,2,3-trimethylbutane. (1)
January 2019, AS Unit 1, Q21(a)(iii) (1 mark): Write the equation for reforming heptane into cycloheptane. Use molecular formulae. State symbols are not required. (1)
January 2019, AS Unit 1, Q21(a)(iv) (2 marks): When petrol is burned in a car engine, oxides of nitrogen are formed. Explain how these compounds result in damage to trees. (2)
January 2019, AS Unit 1, Q21(b)(i) (1 mark): Chlorine radicals are formed in the first step in the mechanism. Cl2 o 2Cl• Name this step in the mechanism. (1)
January 2019, AS Unit 1, Q21(b)(ii) (2 marks): Give the two propagation steps for the formation of chloroheptane. Use molecular formulae. Curly arrows are not required. (2)
January 2019, AS Unit 1, Q21(b)(iii) (1 mark): Give the termination step which forms a hydrocarbon. (1)
January 2019, AS Unit 1, Q21(b)(iv) (2 marks): Explain how some dichloroheptane, C7H14Cl2 , also forms during this reaction. You may include equation(s) in your answer. (2)

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