Pearson Edexcel International GCSE (9–1) · CHEMISTRY · Section
Calculation of enthalpy changes of reaction using bond energies
19 practice questions
Practice questions
11–19 of 19
Question 11
3 marks · Normal
Answer and see the solution →Calculate the enthalpy change () for the reaction:
Bond Energies (kJ/mol) Bond Bond energy / kJ mol^{-1} H–H 436 O=O 498 O–H 464 Question 12
3 marks · Normal
Answer and see the solution →Explain why the reaction between hydrogen and chlorine to form hydrogen chloride is exothermic, making reference to bond energies:
Bond energies (kJ/mol):
Bond Bond energy H–H 436 Cl–Cl 243 H–Cl 432 Question 13
4 marks · Normal
Answer and see the solution →The following data show bond energies for several bonds:
Bond Energies for Calculation Bond Bond Energy / kJ mol^{-1} C–H 413 O=O 498 C=O 743 O–H 464 (a)[1 mark]Consider the equation:
Count and list all the bonds broken in the reactants.
(b)[1 mark]Count and list all the bonds formed in the products.
(c)[1 mark]Calculate the total energy absorbed in breaking the bonds in the reactants.
(d)[1 mark]Calculate the enthalpy change () for the reaction.
Question 14
1 mark · Normal
Answer and check →Which statement is correct about bond energies and enthalpy change in chemical reactions?
- A.Bond making requires energy and is endothermic.
- B.Breaking bonds releases energy and is exothermic.
- C.Bond making releases energy and is exothermic.
- D.Breaking bonds releases energy and is endothermic.
Question 15
2 marks · Normal
Answer and see the solution →State two reasons why calculated enthalpy changes using bond energies are only estimates and not always exactly the same as values from calorimetry experiments.
Question 16
4 marks · Normal
Answer and see the solution →Consider the following reaction:
Given the following bond energies (kJ/mol):
Bond Energies Bond Bond energy C–H 413 F–F 158 C–F 485 H–F 565 (a)[1 mark]List all the bonds to be broken in the reactants.
(b)[1 mark]Calculate the total energy required to break these bonds.
(c)[1 mark]Calculate the total energy released when new bonds are formed in the products.
(d)[1 mark]Calculate the overall enthalpy change (ΔH) for the reaction.
Question 17
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 18
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 19
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.