Lesson 8.3.1

8.3.1 Mean bond enthalpies and enthalpy change of reaction Quiz: Pearson Edexcel Chemistry, Unit 8

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 8.3.1, Mean bond enthalpies and enthalpy change of reaction: 20 multiple choice questions for the Pearson Edexcel Chemistry (9CH0), Unit 8: Energetics I, written with Revision Ninja.

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The 20 questions

  1. What state must species be in when measuring mean bond enthalpy?

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

  2. How is enthalpy change of reaction calculated using mean bond enthalpies?

    • Broken minus formed
    • Formed minus broken
    • Broken plus formed
    • Formed plus broken

  3. Using mean bond enthalpies H-H = 436, Cl-Cl = 242, H-Cl = 431 kJ mol-1, what is the enthalpy change of H2(g) + Cl2(g) -> 2HCl(g)?

    • -184 kJ mol-1
    • -862 kJ mol-1
    • -678 kJ mol-1
    • +184 kJ mol-1

  4. Using C=C = 612, H-H = 436, C-C = 346 and C-H = 413 kJ mol-1, what is the enthalpy change for C2H4(g) + H2(g) -> C2H6(g)?

    • +124 kJ mol-1
    • -124 kJ mol-1
    • -172 kJ mol-1
    • -1048 kJ mol-1

  5. Methane atomisation requires 1660 kJ mol-1 to break all four C-H bonds in CH4(g). What is the mean C-H bond enthalpy?

    • 332 kJ mol-1
    • 1660 kJ mol-1
    • 415 kJ mol-1
    • 830 kJ mol-1

  6. Why are calculations using mean bond enthalpies only approximate?

    • Mass is lost
    • Values are averages
    • Reactions are slow
    • Bonds never break

  7. Using mean bond enthalpies H-H = 436, Br-Br = 193 and H-Br = 366 kJ mol-1, what is the enthalpy change for H2(g) + Br2(g) -> 2HBr(g)?

    • -629 kJ mol-1
    • -732 kJ mol-1
    • -103 kJ mol-1
    • +103 kJ mol-1

  8. What is the enthalpy change when 1500 kJ mol⁻¹ is absorbed and 1620 kJ mol⁻¹ is released?

    • +3120 kJ mol⁻¹
    • -120 kJ mol⁻¹
    • -3120 kJ mol⁻¹
    • +120 kJ mol⁻¹

  9. Which term describes the process of breaking a covalent bond?

    • Isothermal
    • Adiabatic
    • Exothermic
    • Endothermic

  10. Why are bond enthalpies measured specifically in the gaseous state?

    • Avoids intermolecular forces
    • Increases reaction rate
    • Maximises kinetic energy
    • Prevents bond breaking

  11. Using mean bond enthalpies C-H = 413, Cl-Cl = 242, C-Cl = 339 and H-Cl = 431 kJ mol-1, what is the enthalpy change for CH4 + Cl2 -> CH3Cl + HCl, where the reaction breaks one C-H bond and one Cl-Cl bond?

    • -115 kJ mol-1
    • -770 kJ mol-1
    • -655 kJ mol-1
    • +115 kJ mol-1

  12. Why is an enthalpy change calculated from mean bond enthalpies an estimate?

    • Pressures fluctuate
    • Mass changes
    • Temperatures vary
    • Environments vary

  13. Calculate the mean O-H bond enthalpy in water if breaking both O-H bonds of H2O(g) needs 926 kJ mol-1.

    • 463 kJ mol-1
    • 926 kJ mol-1
    • 1852 kJ mol-1
    • 232 kJ mol-1

  14. Given a mean C-H bond enthalpy of 413 kJ mol-1, how much energy is needed to break all the C-H bonds in one mole of ethane, C2H6?

    • 826 kJ
    • 1239 kJ
    • 413 kJ
    • 2478 kJ

  15. What does a positive enthalpy change calculated from bond enthalpies indicate?

    • Irreversible reaction
    • Exothermic reaction
    • Endothermic reaction
    • Rapid reaction

  16. Which bonds are broken during the combustion of hydrogen gas?

    • H-H and O-H
    • H-O and O=O
    • O-H and O=O
    • H-H and O=O

  17. Why does using mean C=O bond enthalpy give an approximate value for CO2?

    • Bonds never break
    • CO2 is liquid
    • Environment differs
    • CO2 is ionic

  18. What occurs to energy when chemical bonds are formed?

    • No energy change
    • Energy is absorbed
    • Mass is lost
    • Energy is released

  19. Using mean bond enthalpies, what is the enthalpy change for 2H2(g) + O2(g) -> 2H2O(g) if H-H = 436, O=O = 498 and O-H = 463 kJ mol-1?

    • -482 kJ mol-1
    • +482 kJ mol-1
    • -1852 kJ mol-1
    • -934 kJ mol-1

  20. What is a main advantage of using mean bond enthalpy data?

    • Ignores activation energy
    • Works for solids
    • Estimates missing data
    • Gives exact results

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