Lesson 4.1.2

4.1.2 Alkanes Quiz: OCR Chemistry, Unit 3

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 4.1.2, Alkanes: 20 multiple choice questions for the OCR Chemistry (H432), Unit 3: Core organic chemistry, written with Revision Ninja.

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The 20 questions

  1. What is the shape around each carbon atom in an alkane molecule?

    • Trigonal planar
    • Tetrahedral
    • Pyramidal
    • Linear

  2. Why do longer chain alkanes have higher boiling points?

    • Stronger covalent bonds
    • Stronger hydrogen bonds
    • Weaker dipole forces
    • Stronger London forces

  3. Why do branched alkanes have lower boiling points than straight-chain isomers?

    • Stronger covalent bonds
    • Weaker London forces
    • Weaker ionic bonds
    • Shorter carbon chains

  4. Which factor causes the low reactivity of alkanes?

    • High bond enthalpy
    • Low activation energy
    • High polarity
    • Weak sigma bonds

  5. What toxic gas forms from incomplete combustion of an alkane with limited oxygen?

    • Chlorine gas
    • Hydrogen gas
    • Carbon dioxide only
    • Carbon monoxide

  6. What is required for the initiation step in alkane chlorination?

    • Infrared radiation
    • Nickel catalyst
    • Ultraviolet light
    • High pressure

  7. What happens to the total number of radicals during a propagation step?

    • Remains constant
    • Doubles each time
    • Increases by one
    • Decreases to zero

  8. What happens to the total number of radicals during a termination step?

    • It decreases
    • It doubles
    • It stays constant
    • It increases

  9. Why does free radical substitution of alkanes produce a mixture of products?

    • Reactions are reversible
    • Further substitution occurs
    • Alkanes are polar
    • Radicals decompose quickly

  10. How many moles of oxygen are needed for the complete combustion of 1 mol of pentane, C5H12?

    • 6
    • 8
    • 12
    • 5

  11. What mass of CO2 forms from complete combustion of 1.00 g of propane, C3H8 (Mr = 44)?

    • 3.00 g
    • 1.00 g
    • 44.0 g
    • 4.00 g

  12. Why are C-H bonds in alkanes considered non-polar?

    • Ionic character dominates
    • Similar electronegativities
    • Large dipoles present
    • Hydrogen is metallic

  13. What role does UV light play in the reaction of methane with chlorine?

    • Acts as catalyst
    • Breaks C-H bonds
    • Inhibits radical formation
    • Breaks Cl-Cl bonds

  14. Which product is the most fully substituted from excess chlorine acting on methane?

    • CH2Cl2
    • CH3Cl
    • CHCl3
    • CCl4

  15. Which term best describes alkanes based on their bonding?

    • Unsaturated hydrocarbons
    • Aromatic compounds
    • Saturated hydrocarbons
    • Polar polymers

  16. What type of bond is formed by direct overlap of orbitals in alkanes?

    • Sigma bond
    • Hydrogen bond
    • Pi bond
    • Dative bond

  17. Why can carbon-carbon single bonds in alkanes rotate freely?

    • High bond enthalpy
    • Presence of pi bonds
    • Symmetrical orbital overlap
    • Weak electrostatic repulsion

  18. Which alkane is a liquid at room temperature?

    • Ethane
    • Octane
    • Propane
    • Methane

  19. How many moles of CO2 form from the complete combustion of 0.10 mol of octane, C8H18?

    • 0.80 mol
    • 1.60 mol
    • 0.40 mol
    • 0.10 mol

  20. Why is carbon monoxide gas dangerous when inhaled by humans?

    • Blocks carbon dioxide
    • Forms toxic acid
    • Binds to haemoglobin
    • Destroys lung tissue

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