Lesson 3.1.4.4

3.1.4.4 Bond enthalpies Quiz: AQA Chemistry, Unit 1

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 3.1.4.4, Bond enthalpies: 20 multiple choice questions for the AQA Chemistry (7405), Unit 1: Physical chemistry, written with Revision Ninja.

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The 20 questions

  1. In which physical state must molecules be when defining mean bond enthalpy?

    • Gaseous state
    • Solid state
    • Aqueous state
    • Liquid state

  2. Breaking bonds is what type of process?

    • Neutral
    • Exothermic
    • Endothermic
    • Isothermal

  3. What type of process is bond making in chemical reactions?

    • Endothermic
    • Athermic
    • Exothermic
    • Isothermal

  4. How is enthalpy change calculated using mean bond enthalpies?

    • Reactants minus products
    • Broken minus formed
    • Products minus reactants
    • Formed minus broken

  5. Mean bond enthalpy is defined as an average taken across what?

    • Liquid solutions
    • Single compound
    • Gaseous elements
    • Various compounds

  6. Which state of matter must substances be in for mean bond enthalpy calculations?

    • Solid phase
    • Gaseous phase
    • Liquid phase
    • Aqueous phase

  7. Why do calculations using mean bond enthalpies give approximate enthalpy changes?

    • Bonds never break
    • Reactions are incomplete
    • Values are averaged
    • Heat is gained

  8. Using H-H = 436, Cl-Cl = 242 and H-Cl = 431 kJ mol-1, what is delta H for H2 + Cl2 -> 2HCl?

    • +184 kJ mol-1
    • -678 kJ mol-1
    • -1109 kJ mol-1
    • -184 kJ mol-1

  9. Using H-H = 436, F-F = 158 and H-F = 562 kJ mol-1, what is delta H for H2 + F2 -> 2HF?

    • +530 kJ mol-1
    • -1124 kJ mol-1
    • -594 kJ mol-1
    • -530 kJ mol-1

  10. Using C-H = 413, Cl-Cl = 242, C-Cl = 328 and H-Cl = 431 kJ mol-1, what is delta H for CH4 + Cl2 -> CH3Cl + HCl?

    • -759 kJ mol-1
    • +104 kJ mol-1
    • -655 kJ mol-1
    • -104 kJ mol-1

  11. Which bond needs the most energy to break: C-C (348), C=C (612) or C≡C (838) kJ mol-1?

    • C=C
    • C≡C
    • All are equal
    • C-C

  12. A reaction is endothermic when bond breaking absorbs how much energy compared to bond making?

    • Less energy
    • Zero energy
    • More energy
    • Equal energy

  13. Using C=C = 612, H-H = 436, C-C = 348 and C-H = 413 kJ mol-1, what is delta H for C2H4 + H2 -> C2H6?

    • -1048 kJ mol-1
    • -1174 kJ mol-1
    • +126 kJ mol-1
    • -126 kJ mol-1

  14. What is the enthalpy change for the formation of H2 gas from H atoms, given H-H = 436 kJ mol-1?

    • +436 kJ mol-1
    • -218 kJ mol-1
    • +218 kJ mol-1
    • -436 kJ mol-1

  15. Which type of thermodynamic process always occurs during bond breaking?

    • Exothermic
    • Isothermal
    • Adiabatic
    • Endothermic

  16. Why does a C–H bond enthalpy differ between methane and ethane?

    • Different oxidation states
    • Different chemical environments
    • Different physical states
    • Different bond orders

  17. Using N≡N = 945, H-H = 436 and N-H = 391 kJ mol-1, what is delta H for N2 + 3H2 -> 2NH3?

    • +93 kJ mol-1
    • -93 kJ mol-1
    • -2253 kJ mol-1
    • -2346 kJ mol-1

  18. Why are mean bond enthalpies only valid for reactions in the gaseous state?

    • Faster reaction rate
    • Higher activation energy
    • Complete combustion occurs
    • No intermolecular forces

  19. Using C=C = 612, H-Cl = 431, C-C = 348, C-H = 413 and C-Cl = 328 kJ mol-1, what is the estimated delta H for C2H4 + HCl -> C2H5Cl?

    • +46 kJ mol-1
    • -1089 kJ mol-1
    • -1043 kJ mol-1
    • -46 kJ mol-1

  20. A reaction needs 1200 kJ to break bonds and releases 1350 kJ when bonds form. What is delta H?

    • -2550 kJ mol-1
    • +150 kJ mol-1
    • -150 kJ mol-1
    • +2550 kJ mol-1

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