Pearson Edexcel International GCSE (9–1) · CHEMISTRY · Section
Why do reactions either give out or absorb heat?
19 practice questions
Practice questions
1–3 of 3 · Hard
Question 1
2 marks · Hard
Answer and see the solution →A reaction is found to be exothermic overall. Explain, in terms of bond energies, why this is the case.
Question 2
5 marks · Hard
Answer and see the solution →When carbon monoxide reacts with oxygen, the following reaction occurs:
You are given the following average bond energies:
Bond Average bond energy (kJ/mol) C≡O 1072 O=O 498 C=O (in CO2) 805 (a)[2 marks]List one type of bond broken and one type of bond formed in this reaction.
(b)[1 mark]Explain why this reaction is exothermic, using bond energies.
(c)[2 marks]Calculate the enthalpy change, ΔH, for the reaction, using the bond energies in the table. Show your working and give the answer in kJ/mol (for the equation as written).
Question 3
2 marks · Hard
Answer and see the solution →Describe, in terms of bonds and energy, what happens during an endothermic reaction.