Pearson Edexcel International GCSE (9–1) · CHEMISTRY · Chapter
Energetics
117 practice questions
Topics covered
- Exothermic reactions19 practice questions
- Endothermic reactions19 practice questions
- Measuring enthalpy changes of reactions19 practice questions
- Calorimetry experiments for determining the enthalpy changes of reactions18 practice questions
- Why do reactions either give out or absorb heat?19 practice questions
- Calculation of enthalpy changes of reaction using bond energies19 practice questions
Practice questions
41–48 of 48 · Normal
Question 41
2 marks · Normal
Answer and see the solution →State the meaning of the term 'bond energy' and give the unit in which it is measured.
Question 42
4 marks · Normal
Answer and see the solution →The reaction between ethane and chlorine is represented by the following equation:
Use the bond energies given below for your calculations.
Bond Energies Bond Bond energy / kJ mol^{-1} C–H 413 C–C 348 C–Cl 338 Cl–Cl 243 H–Cl 432 (a)[1 mark]List all bonds that are broken and all bonds that are formed in this reaction.
(b)[1 mark]Calculate the total energy required to break the bonds in the reactants.
(c)[1 mark]Calculate the total energy released when new bonds are formed in the products.
(d)[1 mark]Calculate the enthalpy change () for the reaction. State whether the reaction is exothermic or endothermic.
Question 43
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 44
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 45
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 46
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 47
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 48
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.