Lesson 3.3.4.2

3.3.4.2 Addition reactions of alkenes Quiz: AQA Chemistry, Unit 3

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 3.3.4.2, Addition reactions of alkenes: 20 multiple choice questions for the AQA Chemistry (7405), Unit 3: Organic chemistry, written with Revision Ninja.

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The 20 questions

  1. What type of mechanism do alkenes undergo with HBr?

    • Elimination
    • Nucleophilic substitution
    • Electrophilic addition
    • Free-radical substitution

  2. What is the first step in the electrophilic addition of HBr to ethene?

    • The C=C pi bond attacks H of HBr, forming a carbocation and Br-
    • HBr breaks into radicals under dark conditions
    • Br- attacks the C=C bond directly with no intermediate
    • Ethene loses a hydrogen atom to form ethyne

  3. What is the product of the reaction of ethene with bromine water?

    • 1,2-dibromoethane
    • Tribromoethane
    • Bromoethene
    • Ethanol

  4. Which reagent is used to test for unsaturation in an organic compound?

    • Lime water
    • Sodium carbonate
    • Bromine water
    • Dilute hydrochloric acid

  5. What is the major product of adding HBr to propene?

    • 2-bromopropane
    • Bromoethane
    • 1-bromopropane
    • Propan-2-ol

  6. What is the minor product of adding HBr to propene?

    • Propene only
    • 1-bromopropane
    • 2-bromopropane
    • Bromoethane

  7. Which carbocation is the most stable?

    • Secondary only
    • Tertiary
    • Primary
    • Methyl only

  8. Why is 2-bromopropane the major product from propene and HBr?

    • It is produced without any intermediate
    • It forms via the less stable primary carbocation
    • It is produced by a free-radical reaction only
    • It forms via the more stable secondary carbocation

  9. Which alkene gives only one product when reacted with HBr?

    • Ethene
    • But-1-ene
    • 2-methylpropene
    • Propene

  10. What is the product of adding H2SO4 to ethene followed by hydrolysis?

    • Ethanol
    • Ethyne
    • Ethanoic acid
    • Ethane

  11. Which electrophile is formed in the addition of Br2 to an alkene?

    • A bromonium ion or polarised Br2 species
    • A chloride ion
    • A bromide ion
    • A hydroxide ion

  12. Why is the addition of bromine to an alkene described as electrophilic?

    • Br2 is a nucleophile that donates electrons to the C=C bond
    • The reaction involves only the removal of H+
    • Bromine is a radical that attacks the C=C bond
    • Br2 is polarised and the electron-rich C=C bond is attacked by an electron-pair acceptor

  13. Which product forms when HBr adds to but-1-ene in the major pathway?

    • Butan-1-ol
    • 1-bromobutane
    • 2-bromobutane
    • But-2-ene

  14. What is the name of the rule used to predict the major product of electrophilic addition to unsymmetrical alkenes?

    • Avogadro's law
    • Markovnikov's rule
    • Le Chatelier's principle
    • Hess's law

  15. What is the role of H2SO4 in the addition of H2SO4 to an alkene?

    • It is an electrophile that adds H+ to the C=C bond
    • It is an oxidising agent that adds oxygen
    • It is a radical initiator
    • It is a nucleophile that removes Br from the alkene

  16. What is the balanced equation for the addition of Br2 to ethene?

    • C2H4 + Br2 -> C2H4Br2
    • C2H4 + Br2 -> C2H2Br2 + H2
    • C2H4 + 2Br2 -> C2H4Br4
    • C2H4 + Br2 -> C2H3Br + HBr

  17. Explain the reason for the major and minor product formation in addition reactions of unsymmetrical alkenes.

    • The reaction involves only radicals so products are random
    • The more stable carbocation intermediate forms preferentially, so the major product results from it
    • The minor product is always more stable than the major product
    • Both products form from identical intermediates with equal stability

  18. Explain why a tertiary carbocation is more stable than a primary carbocation.

    • Alkyl groups withdraw electron density, making the positive carbon more concentrated
    • The tertiary carbocation has no positive charge
    • Alkyl groups donate electron density to the positive carbon, spreading and stabilising the charge
    • Primary carbocations contain more hydrogen atoms that repel the charge

  19. A student adds bromine water to an unknown liquid and the orange colour disappears. What does this show?

    • The compound is an ionic salt
    • The compound is an acid that neutralises bromine
    • The compound is saturated and contains only C-C single bonds
    • The compound is unsaturated and contains a C=C bond

  20. Explain why the reaction of alkenes with bromine water is useful as a test for unsaturation.

    • Alkanes change bromine water to a blue solution, unlike alkenes
    • Bromine water produces a precipitate only with alkanes
    • The orange bromine is decolourised rapidly by addition across C=C bonds, while saturated alkanes do not react
    • Bromine water reacts equally with all organic compounds

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