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
81–90 of 117
Question 81
1 mark · Easy
Answer and see the solution →What must occur to the bonds in a molecule for a reaction to absorb heat from the surroundings?
Question 82
3 marks · Easy
Answer and see the solution →The reaction below takes place:
Answer the following questions:
(a)[1 mark]State one bond broken during this reaction.
(b)[1 mark]State one bond formed during this reaction.
(c)[1 mark]Explain why energy is required for this reaction to occur.
Question 83
2 marks · Easy
Answer and see the solution →Hydrogen reacts with bromine to make hydrogen bromide:
Bond Bond energy (kJ/mol) H–H 436 Br–Br 193 H–Br 366 Calculate the enthalpy change (ΔH) for the reaction. Include units and sign.
Question 84
2 marks · Normal
Answer and see the solution →Explain what happens to energy during the breaking and making of bonds in a chemical reaction.
Question 85
4 marks · Normal
Answer and see the solution →Ammonia is synthesised by reacting nitrogen and hydrogen:
(a)[2 marks]State which bonds must be broken and which bonds must be formed in the reaction above.
(b)[2 marks]Explain, in terms of energy, why this reaction can be exothermic.
Question 86
3 marks · Normal
Answer and see the solution →The reaction below occurs:
Bond energies (in kJ/mol): H–H = 436, Cl–Cl = 243, H–Cl = 431
Calculate the overall enthalpy change (ΔH) for the reaction.
Question 87
3 marks · Normal
Answer and see the solution →Describe, using bond breaking and bond making, how you can tell if a chemical reaction will be exothermic or endothermic.
Question 88
4 marks · Normal
Answer and see the solution →The table below gives average bond energies.
Average bond energies Bond Bond energy (kJ/mol) C–H 413 O=O 498 C=O 799 (a)[2 marks]List the bonds broken and bonds formed when methane reacts with oxygen to form carbon dioxide and water.
(b)[2 marks]Suggest, using the bond energies, why this reaction is highly exothermic.
Question 89
1 mark · Normal
Answer and check →Which statement best describes what happens during bond formation in a chemical reaction?
- A.Energy is released to the surroundings.
- B.Energy is absorbed from the surroundings.
- C.The temperature always decreases.
- D.No energy change occurs.
Question 90
2 marks · Normal
Answer and see the solution →State what must occur, in terms of bonds, for a reaction to be endothermic.