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Pearson Edexcel International GCSE (9–1) · CHEMISTRY · Section

Calculation of enthalpy changes of reaction using bond energies

19 practice questions

Start practising (8 questions)

Practice questions

1–8 of 8 · Normal

  1. Question 1

    2 marks · Normal

    State the meaning of the term 'bond energy' and give the unit in which it is measured.

    Answer and see the solution →

  2. Question 2

    4 marks · Normal

    The reaction between ethane and chlorine is represented by the following equation:

    Use the bond energies given below for your calculations.

    Bond Energies
    BondBond energy / kJ mol^{-1}
    C–H413
    C–C348
    C–Cl338
    Cl–Cl243
    H–Cl432
    (a)

    List all bonds that are broken and all bonds that are formed in this reaction.

    [1 mark]
    (b)

    Calculate the total energy required to break the bonds in the reactants.

    [1 mark]
    (c)

    Calculate the total energy released when new bonds are formed in the products.

    [1 mark]
    (d)

    Calculate the enthalpy change () for the reaction. State whether the reaction is exothermic or endothermic.

    [1 mark]
    Answer and see the solution →

  3. Question 3

    3 marks · Normal

    Calculate the enthalpy change () for the reaction:

    Bond Energies (kJ/mol)
    BondBond energy / kJ mol^{-1}
    H–H436
    O=O498
    O–H464
    Answer and see the solution →

  4. Question 4

    3 marks · Normal

    Explain why the reaction between hydrogen and chlorine to form hydrogen chloride is exothermic, making reference to bond energies:

    Bond energies (kJ/mol):

    BondBond energy
    H–H436
    Cl–Cl243
    H–Cl432
    Answer and see the solution →

  5. Question 5

    4 marks · Normal

    The following data show bond energies for several bonds:

    Bond Energies for Calculation
    BondBond Energy / kJ mol^{-1}
    C–H413
    O=O498
    C=O743
    O–H464
    (a)

    Consider the equation:

    Count and list all the bonds broken in the reactants.

    [1 mark]
    (b)

    Count and list all the bonds formed in the products.

    [1 mark]
    (c)

    Calculate the total energy absorbed in breaking the bonds in the reactants.

    [1 mark]
    (d)

    Calculate the enthalpy change () for the reaction.

    [1 mark]
    Answer and see the solution →

  6. Question 6

    1 mark · Normal

    Which statement is correct about bond energies and enthalpy change in chemical reactions?

    1. A.Bond making requires energy and is endothermic.
    2. B.Breaking bonds releases energy and is exothermic.
    3. C.Bond making releases energy and is exothermic.
    4. D.Breaking bonds releases energy and is endothermic.
    Answer and check →

  7. Question 7

    2 marks · Normal

    State two reasons why calculated enthalpy changes using bond energies are only estimates and not always exactly the same as values from calorimetry experiments.

    Answer and see the solution →

  8. Question 8

    4 marks · Normal

    Consider the following reaction:

    Given the following bond energies (kJ/mol):

    Bond Energies
    BondBond energy
    C–H413
    F–F158
    C–F485
    H–F565
    (a)

    List all the bonds to be broken in the reactants.

    [1 mark]
    (b)

    Calculate the total energy required to break these bonds.

    [1 mark]
    (c)

    Calculate the total energy released when new bonds are formed in the products.

    [1 mark]
    (d)

    Calculate the overall enthalpy change (ΔH) for the reaction.

    [1 mark]
    Answer and see the solution →