Pearson Edexcel International GCSE (9–1) · CHEMISTRY · Section
Calculation of enthalpy changes of reaction using bond energies
19 practice questions
Practice questions
1–3 of 3 · Hard
Question 1
2 marks · Hard
Answer and see the solution →The following reaction occurs:
Bond energies (in kJ/mol):
Bond Bond energy / kJ mol^{-1} H–H 436 F–F 158 H–F 565 Calculate the enthalpy change (ΔH) for the reaction using the bond energies given.
Question 2
5 marks · Hard
Answer and see the solution →Chloroethane can be made by reacting ethene with hydrogen chloride:
Bond energies (kJ/mol) Bond Bond energy / kJ mol^{-1} C=C 612 C–C 348 C–H 413 H–Cl 432 C–Cl 338 (a)[2 marks]Write down all the bonds broken and all the bonds formed in this reaction.
(b)[3 marks]Calculate the enthalpy change (ΔH), in kJ/mol, for the reaction using the bond energies provided. Show your working and give your answer to the nearest kJ/mol.
Question 3
2 marks · Hard
Answer and see the solution →A student calculates the enthalpy change for the following reaction using average bond energies:
Bond energies (kJ/mol):
Bond Bond energy / kJ mol^{-1} Cl–Cl 243 H–S 363 H–Cl 432 State the total energy required to break all the bonds in the reactants, and the total energy released when new bonds form in the products. Show your calculations.