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
31–40 of 48 · Normal
Question 31
2 marks · Normal
Answer and see the solution →State the two steps needed to calculate the molar enthalpy change (ΔH) from calorimetry data.
Question 32
4 marks · Normal
Answer and see the solution →Neutralisation experiments using polystyrene cups are often used to calculate enthalpy changes of reaction.
(a)[1 mark]Give one reason why a polystyrene cup is used instead of a metal can.
(b)[1 mark]Suggest one way the experiment might underestimate the enthalpy change.
(c)[1 mark]State one possible way to minimise errors from heat lost during the experiment.
(d)[1 mark]Explain how using a lid can help improve the accuracy of a calorimetry result.
Question 33
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 34
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 35
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 36
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 37
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 38
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 39
2 marks · Normal
Answer and see the solution →State what must occur, in terms of bonds, for a reaction to be endothermic.
Question 40
4 marks · Normal
Answer and see the solution →Read the following reaction:
You are given these average bond energies (kJ/mol): S=O = 523, O=O = 498
a) Write down all bonds that are broken and formed during the reaction.
b) Explain, using these bond energies, what determines whether the reaction is exothermic or endothermic.
(a)[2 marks]List all bonds broken and formed.
(b)[2 marks]Explain, using bond energies, what determines if the reaction is exothermic or endothermic.