Arenes: Edexcel International A Level Chemistry questions

Every Edexcel International A Level Chemistry exam question on Arenes (specification points 18.1–18.6), 2019–2025, with its mark scheme and examiner’s report.

All 82 questions on Arenes, as a list

June 2025, Unit 5, Q16(a)(iii) (2 marks): Explain why the bond enthalpy value calculated in (a)(ii) is not the exact mean of the carbon-carbon double bond and carbon-carbon single bond enthalpies that w
June 2025, Unit 5, Q16(b) (2 marks): Describe how all the carbon-carbon bonds in benzene are formed. (2)
June 2025, Unit 5, Q16(c) (2 marks): State one chemical property and one physical property of benzene which would not be shown by the compound with the Kekulé structure. (2)
June 2025, Unit 5, Q20(d)(i) (1 mark): Concentrated nitric and sulfuric acid are used to produce NO 2 to initiate the reaction. + Write the equation for the production of NO 2 . (1)
June 2025, Unit 5, Q20(d)(ii) (5 marks): Complete the reaction mechanism to form 5-nitrosalicylic acid, naming the reaction mechanism. (5) Reaction mechanism O OH OH NO2 +
June 2025, Unit 5, Q20(d)(iii) (3 marks): Explain why benzenecarboxylic acid requires concentrated nitric and sulfuric acids for nitration while salicylic acid may be nitrated using dilute nitric acid.
June 2025 (A), Unit 5, Q10 (1 mark): Benzene is nitrated using a mixture of concentrated nitric and sulfuric acids. In this reaction, the sulfuric acid A dissolves both benzene and nitric acid B fo
June 2025 (A), Unit 5, Q11 (1 mark): Which is the best technique to show that the carbon‑carbon bonds in benzene are all the same length? A infrared spectroscopy B mass spectrometry C high resoluti
June 2025 (A), Unit 5, Q13 (1 mark): The reaction between chlorine and phenol is faster than that between chlorine and benzene. Which is the best explanation for this? A the carbon‑oxygen bond is w
June 2025 (A), Unit 5, Q17(c)(i) (1 mark): Identify, by name or formula, the reagent used in Reaction 1. (1)
June 2025 (A), Unit 5, Q18(a) (4 marks): Draw the mechanism for the reaction in Step 1 to produce J, including the formation of the electrophile. (4)
January 2025, Unit 5, Q22 (6 marks): * 22 Compare and contrast the bromination of benzene and the bromination of phenol. Include equations in your answer. Detailed mechanisms are not required. (6)
January 2025, Unit 5, Q23(b)(i) (2 marks): Identify, by name or formula, the two reagents needed for Step 1. (2)
January 2025, Unit 5, Q23(b)(ii) (5 marks): For Step 2, draw the mechanism for this reaction, including the formation of a suitable electrophile and the regeneration of the catalyst. Include curly arrows.
January 2025, Unit 6, Q2(a) (2 marks): A student suggested using iron as a catalyst in Step 1. Explain why it is not needed in the reaction with phenol, even though chlorination of other aryl compoun
October 2024, Unit 5, Q10(a) (1 mark): Evidence for the aromaticity of this compound is that the carbon-carbon bonds in the ten-carbon ring (1) A alternate in length between single and double bonds B
October 2024, Unit 5, Q10(b) (1 mark): The aromaticity is due to the formation of pi (π) bonds as a result of overlap of (1) A s and p orbitals B p and d orbitals C p orbitals D d orbitals
October 2024, Unit 5, Q19(b)(i) (5 marks): Draw the mechanism for this reaction, using appropriate curly arrows. Include equations showing the formation of the electrophile and the regeneration of the ca
October 2024, Unit 5, Q19(b)(ii) (1 mark): Give a reason why the yield of the raspberry ketone by this method is not high. (1)
June 2024, Unit 5, Q7 (1 mark): Which type of data is not used as evidence for the structure or stability of the benzene ring? A infrared spectroscopy B mass spectrometry C thermochemical D X‑
June 2024, Unit 5, Q8 (1 mark): The formation of nitrobenzene requires benzene and concentrated nitric and sulfuric acids. Which is an equation for the reaction to form the electrophile? A HNO
June 2024, Unit 5, Q15(a)(i) (1 mark): The sulfonation of phenol is similar to the sulfonation of benzene. Suggest the reagent(s) required for Reaction A. (1)
June 2024, Unit 5, Q15(a)(ii) (1 mark): Deduce the structure of intermediate compound B. (1)
June 2024, Unit 5, Q15(a)(iii) (3 marks): Explain why the reaction of chlorine with phenol occurs under milder conditions than the reaction of chlorine with benzene. (3)
June 2024, Unit 5, Q17(a) (3 marks): The first step of the synthesis is the formation of methylbenzene, from benzene and chloromethane. Draw the mechanism of this reaction. Equations for the format
January 2024, Unit 5, Q13(a) (2 marks): Explain how the results of X‑ray diffraction experiments on benzene suggest a delocalised structure rather than the Kekulé structure. (2)
January 2024, Unit 5, Q13(b) (2 marks): The compound 1,2‑dichlorobenzene exists as only one structure. Explain how this supports the delocalised structure of benzene rather than the Kekulé structure.
January 2024, Unit 5, Q13(c) (1 mark): State how the enthalpy changes of hydrogenation for cyclohexene and benzene provide evidence for the delocalised structure. ΔH = –118 kJ mol–1 + H2 → + 3H2 → ΔH
January 2024, Unit 5, Q13(d) (3 marks): Describe the structure of benzene in terms of the atomic orbitals involved, the bonds formed and the delocalised electrons. (3)
January 2024, Unit 5, Q14(a)(i) (2 marks): Identify, by name or formula, the second reagent and the electrophile. (2)
January 2024, Unit 5, Q14(a)(ii) (3 marks): Draw the mechanism for the reaction between the electrophile and benzene to form nitrobenzene. (3)
January 2024, Unit 5, Q14(e) (2 marks): Another painkiller, paracetamol, can be synthesised from phenol in a similar sequence. Phenol is nitrated by dilute nitric acid. H NO2 NH2 N O HO HO HO HO pheno
October 2023, Unit 5, Q15(a) (1 mark): Step 1 takes place using a mixture of concentrated nitric acid and concentrated sulfuric acid at 55°C. Why is the reaction not carried out at 80°C? (1) A furthe
October 2023, Unit 5, Q20(a)(i) (4 marks): Draw the mechanism for this reaction, including the formation of the electrophile. (4)
October 2023, Unit 5, Q20(a)(ii) (6 marks): Compare and contrast the reaction of benzene with bromine with the reactions of cyclohexene with bromine and of phenol with bromine. Include reasons for any dif
June 2023, Unit 5, Q15 (1 mark): What is the total number of delocalised electrons in anthracene? anthracene A 6 B 10 C 14 D 18
June 2023, Unit 5, Q16 (1 mark): Which statement explains why bromine reacts more readily with phenol than with benzene? A the O H bond in phenol is polar B the oxygen atom in phenol is very el
June 2023, Unit 5, Q23 (6 marks): *23 Some thermochemical, X-ray diffraction and bromination information on benzene and cyclohexene is shown. Thermochemical data Compound Enthalpy of hydrogenati
June 2023, Unit 5, Q25(d)(i) (4 marks): Give the mechanism for Step 1. Include an equation for the formation of the electrophile. (4)
June 2023, Unit 5, Q25(d)(ii) (2 marks): A low yield of 2,6-dimethylnitrobenzene is obtained in Step 1 due to the formation of additional organic products. Give possible structures for two additional o
June 2023, Unit 6, Q4(b) (1 mark): Side products form if the temperature rises above 15 °C in Step 4. Give the structure of one side product that may form. (1)
January 2023, Unit 5, Q19(a)(i) (3 marks): Draw a mechanism for the reaction to form 2-nitrophenol. + is the electrophile. Assume that NO2 (3)
January 2023, Unit 5, Q19(a)(ii) (2 marks): Benzene requires a mixture of concentrated nitric acid and concentrated sulfuric acid at 60 °C to form nitrobenzene. Explain why phenol requires milder conditio
October 2022, Unit 5, Q10 (1 mark): How many σ bonds and π bonds are there in a molecule of benzene? σ bonds π bonds A 6 3 B 6 6 C 12 3 D 12 6
October 2022, Unit 5, Q11 (1 mark): Benzene reacts with fuming sulfuric acid to form benzenesulfonic acid. Fuming sulfuric acid is A sulfuric acid with a concentration of 98 % B pure sulfuric acid
October 2022, Unit 5, Q20 (6 marks): *20 Delocalised electron systems are important in determining the chemical properties of some compounds. Compare and contrast the chemical reactions of bromine
October 2022, Unit 5, Q23(c)(i) (1 mark): Write an equation for the formation of the electrophile from methanoyl chloride. Use displayed formulae. (1)
October 2022, Unit 5, Q23(c)(ii) (3 marks): Draw the mechanism of the formation of benzaldehyde from benzene using the electrophile from (c)(i). (3)
June 2022, Unit 5, Q11 (1 mark): Which is correct for the reaction of bromine with phenol when compared with benzene? Reactivity of phenol Electron density of the ring in phenol A more reactive
June 2022, Unit 5, Q12(a)(i) (2 marks): Identify two errors in the mechanism by circling them. (2)
June 2022, Unit 5, Q12(a)(ii) (2 marks): State how the errors identified in (a)(i) should be corrected. Justify your answer in terms of the structures involved. (2)
June 2022, Unit 5, Q12(b) (1 mark): Give a reason why it is important to keep the temperature below 30 °C in Step 2. (1)
June 2022, Unit 5, Q12(c) (1 mark): State the type of reaction in Step 3. (1)
January 2022, Unit 5, Q6(b) (1 mark): What type of reaction takes place? (1) A nucleophilic addition B nucleophilic substitution C electrophilic addition D electrophilic substitution
January 2022, Unit 5, Q6(c) (1 mark): Which expression shows the mass in grams of 2,4,6‑trinitromethylbenzene formed from 10 g of methylbenzene if the yield of the reaction is 85 %? [Mr values: meth
January 2022, Unit 5, Q16(b)(i) (5 marks): In Step 1, benzoic acid reacts with concentrated nitric acid to form 3‑nitrobenzoic acid. HO O HO O C C conc. H2SO4 catalyst + concentrated HNO3 NO2 benzoic aci
October 2021, Unit 5, Q11 (1 mark): Which of these could not be formed when excess benzene is heated with trichloromethane, CHCl3, in the presence of an aluminium chloride catalyst? Cl A B Cl Cl C
October 2021, Unit 5, Q12 (1 mark): What is the molar mass, in g mol–1, of the organic product when phenol reacts with excess bromine water? A 156.9 B 172.9 C 330.7 D 488.5
October 2021, Unit 5, Q19(a) (2 marks): Describe a chemical test, including the result, that could distinguish the Dewar structure from benzene. (2)
October 2021, Unit 5, Q19(b) (2 marks): State one similarity and one difference you would expect in the low resolution proton NMR spectrum of the Ladenburg structure and that of benzene. You must incl
October 2021, Unit 5, Q19(c) (2 marks): Explain how X‑ray diffraction shows that benzene has a delocalised structure and not a Kekulé structure. (2)
October 2021, Unit 5, Q19(d)(i) (2 marks): Draw a labelled enthalpy level diagram showing the relative thermodynamic stability of the Ladenburg structure, the Dewar structure and benzene. Include the ent
October 2021, Unit 5, Q19(d)(ii) (1 mark): Give a possible reason why the isomerisation of the Dewar structure to benzene has a lower activation energy than that of the Ladenburg structure to benzene. (1
October 2021, Unit 5, Q19(e) (2 marks): The enthalpy change of hydrogenation of hex‑3‑ene is –118 kJ mol–1. + H2 The table shows the enthalpy changes of hydrogenation of two further alkenes containing
October 2021, Unit 5, Q19(f)(i) (2 marks): Draw the skeletal formulae of three different arenes with the formula CH3COC6H4CH3 . (2)
October 2021, Unit 5, Q19(f)(iii) (4 marks): Complete the diagram, including curly arrows, to show the mechanism for the formation of compound X in this reaction. Include an equation for the regeneration o
June 2021, Unit 5, Q9 (1 mark): Benzene is sometimes represented by a Kekulé structure. Kekulé structure of benzene If this were the only structure of benzene, what would be the total number o
June 2021, Unit 5, Q10 (1 mark): What is the product when benzene reacts with fuming sulfuric acid? O S A O O O S OH B O O C S OH OH O D S OH O Use this space for any rough working. Anything yo
June 2021, Unit 5, Q20(a)(i) (2 marks): Using the standard enthalpies of combustion of cyclohexene and cyclohexa-1,4-diene, calculate a value for the enthalpy of combustion of the theoretical compound
June 2021, Unit 5, Q20(a)(ii) (3 marks): Explain the difference between the enthalpy of combustion of ‘cyclohexa-1,3,5-triene’ calculated in (a)(i) and the enthalpy of combustion of benzene given in th
June 2021, Unit 5, Q20(b) (4 marks): Bromine reacts with cyclohexene to form 1,2-dibromocyclohexane, and with benzene to form bromobenzene. Compare and contrast these reactions, considering the typ
June 2021, Unit 5, Q20(c)(i) (1 mark): Identify, by name or formula, the organic product when phenol reacts with excess bromine. (1)
June 2021, Unit 5, Q20(c)(ii) (2 marks): Explain why bromine reacts much faster with phenol than with benzene. (2)
January 2021, Unit 5, Q10 (1 mark): The delocalised electrons in benzene result from the overlap of A s orbitals to form σ bonds B s orbitals to form π bonds C p orbitals to form σ bonds D p orbit
January 2021, Unit 5, Q11 (1 mark): The reaction of ethene with bromine occurs under normal laboratory conditions but the reaction of benzene with bromine to form bromobenzene requires heat and th
January 2021, Unit 5, Q24(a)(i) (3 marks): The bonding represented by this diagram of caffeine differs from that given in the passage. Explain what this diagram indicates about the bonding in caffeine, s
January 2021, Unit 5, Q24(c)(i) (5 marks): A student suggested that caffeic acid could be synthesised by an electrophilic substitution of 1,2-dihydroxybenzene. Draw the mechanism of this electrophilic su
October 2020, Unit 5, Q1 (1 mark): The enthalpy change of hydrogenation of cyclohexene is −120 kJ mol−1. + H2 What is the approximate enthalpy change of hydrogenation of benzene, in kJ mol−1? A −
October 2020, Unit 5, Q2 (1 mark): Which orbitals overlap to form the ring of delocalised electrons in benzene and what type of bond is formed? Orbitals overlapping Type of bond A p π B p σ C s a
October 2020, Unit 5, Q3 (1 mark): Which reagent and catalyst will convert benzene into phenylethanone? O C CH3 Reagent Catalyst A ethanal aluminium chloride B ethanal platinum C ethanoyl chlorid
October 2020, Unit 5, Q5 (1 mark): How many isomers containing a benzene ring are there with the molecular formula C6H3(NO2)2OH? A 4 B 5 C 6 D 7
October 2020, Unit 5, Q22(a)(i) (3 marks): Benzene is converted into nitrobenzene in Step 1 using a mixture of concentrated nitric acid and concentrated sulfuric acid. The electrophile is NO2 + . A stude

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