Pearson Edexcel International GCSE (9–1) · CHEMISTRY · Section
Exothermic reactions
19 practice questions
Practice questions
1–3 of 3 · Hard
Question 1
2 marks · Hard
Answer and see the solution →Hydrogen peroxide can be decomposed to form water and oxygen gas. When manganese(IV) oxide is added to hydrogen peroxide solution in a test tube, you notice that the sides of the test tube become noticeably warmer.
Explain, in terms of energy transfer, why this reaction is classified as exothermic.
Question 2
5 marks · Hard
Answer and see the solution →The decomposition of a certain substance is shown by the energy profile diagram below.
(a)[0 marks]Energy profile diagram for a chemical reaction; energies in kJ/mol (b)[2 marks]State whether this reaction is exothermic or endothermic, and explain your answer using the energy values from the diagram.
(c)[2 marks]Calculate the value of ΔH (in kJ/mol) for this reaction using the energy profile diagram.
(d)[1 mark]The activation energy for the reaction is the energy difference between the reactants and the highest point on the diagram. Use the diagram to state the value of the activation energy for this reaction.
Question 3
2 marks · Hard
Answer and see the solution →A student says that 'all reactions which produce heat and raise the temperature are exothermic.' Give one example of a reaction that is exothermic, and explain how the energy changes in this type of reaction.