Lesson 17A.1

17A.1 Chirality, optical isomers and racemic mixtures Quiz: Pearson Edexcel Chemistry, Unit 17

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 17A.1, Chirality, optical isomers and racemic mixtures: 20 multiple choice questions for the Pearson Edexcel Chemistry (9CH0), Unit 17: Organic Chemistry II, written with Revision Ninja.

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The 20 questions

  1. What structural feature makes an organic molecule chiral in the simplest case?

    • Chiral centre
    • Polar bond
    • Planar ring
    • Double bond

  2. Which phrase best describes the structural relationship between two optical isomers?

    • Geometric cis-trans forms
    • Same structural formula
    • Superimposable mirror images
    • Non-superimposable mirror images

  3. What effect does a single optical isomer have on plane-polarised light?

    • Rotates the plane
    • Splits the light
    • Absorbs the light
    • Reflects the light

  4. Why does a racemic mixture show no overall optical activity?

    • Contains no enantiomers
    • Rotates light twice
    • Equal opposite rotations
    • Absorbs light completely

  5. Why does a racemic mixture show no net rotation of plane-polarised light?

    • Equal opposite rotations
    • Light is absorbed
    • No optical isomers
    • Only one enantiomer

  6. Which molecule contains a single chiral centre?

    • 2-bromopropane
    • 2-bromobutane
    • 2-methylpropan-2-ol
    • 1-bromobutane

  7. How many stereoisomers does a molecule with two chiral centres have, if it has no meso form?

    • 2
    • 3
    • 4
    • 8

  8. Lactic acid (2-hydroxypropanoic acid) has one chiral centre. How many optical isomers does it have?

    • 3
    • 1
    • 4
    • 2

  9. Which mechanism produces a racemic mixture from an optically active halogenoalkane?

    • Electrophilic addition
    • Free radical substitution
    • SN2 substitution
    • SN1 substitution

  10. What stereochemical outcome occurs during SN2 hydrolysis of a single enantiomer halogenoalkane?

    • Formation of mesomer
    • Inversion of configuration
    • Retention of configuration
    • Complete racemisation

  11. A compound rotates plane-polarised light by +10 degrees. Its enantiomer rotates it by which value under the same conditions?

    • -10 degrees
    • +20 degrees
    • 0 degrees
    • +10 degrees

  12. What name is given to an achiral molecule containing multiple chiral centres?

    • Meso compound
    • Racemic mixture
    • Optical isomer
    • Enantiomer

  13. What feature defines a chiral carbon centre in an organic molecule?

    • Planar carbon backbone
    • Four different groups
    • Carbon-carbon double bond
    • Three different groups

  14. What optical activity is shown by products formed purely from achiral reactants?

    • Optically inactive
    • Laevorotatory only
    • Dextrorotatory only
    • High optical purity

  15. Why do two enantiomers have identical melting and boiling temperatures?

    • Identical optical rotations
    • Different molecular masses
    • Same functional groups
    • Identical intermolecular forces

  16. What effect does a racemic mixture have on plane-polarised light?

    • Anticlockwise rotation only
    • Clockwise rotation only
    • Complete light absorption
    • No net rotation

  17. What happens to optical rotation during SN1 hydrolysis of an optically active halogenoalkane?

    • Increases to maximum
    • Decreases to zero
    • Reverses direction completely
    • Remains completely unchanged

  18. What key structural feature defines a chiral molecule?

    • Planar carbon skeleton
    • Internal symmetry plane
    • Superimposable mirror image
    • Non-superimposable mirror image

  19. What value of optical rotation is measured for a racemic mixture solution?

    • Variable rotation
    • Positive rotation
    • Zero degrees
    • Negative rotation

  20. Which molecule is achiral?

    • 2-methylpropan-2-ol
    • 2-chlorobutane
    • 2-hydroxypropanoic acid
    • 2-bromopentane

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