Pearson Edexcel International GCSE (9–1) · CHEMISTRY · Section
Exothermic reactions
19 practice questions
Practice questions
1–8 of 8 · Normal
Question 1
2 marks · Normal
Answer and see the solution →State whether the following reactions are exothermic or endothermic. Give a reason for each answer.
(a)[1 mark]Dissolving potassium nitrate in water causes the temperature of the solution to fall.
(b)[1 mark]Combustion of methane gas produces heat and a flame.
Question 2
4 marks · Normal
Answer and see the solution →The diagram below shows an incomplete energy profile for a chemical reaction.
Incomplete energy profile diagram for a reaction (a)[2 marks]On the diagram, draw and label:
(i) The activation energy (Ea) as an arrow.
(ii) The energy change (ΔH) as an arrow.
(b)[2 marks]State whether this reaction is exothermic or endothermic and give a reason.
Question 3
3 marks · Normal
Answer and see the solution →Describe how the energy profile diagram of an exothermic reaction differs from that of an endothermic reaction. Your answer should refer to the relative positions of reactants and products and the direction of energy change.
Question 4
4 marks · Normal
Answer and see the solution →The table shows temperature changes observed in four different reactions:
Temperature changes in different reactions Reaction Temperature change (°C) A: Displacement reaction +16 B: Dissolving ammonium chloride -8 C: Combustion of butane +22 D: Neutralisation reaction +7 (a)[2 marks]Identify the two exothermic reactions.
(b)[2 marks]Explain your answer.
Question 5
1 mark · Normal
Answer and check →Which statement about the energy profile diagram for an exothermic reaction is correct?
- A.The products are at a higher energy level than the reactants.
- B.The activation energy arrow points downward from products to reactants.
- C.The reactants are at a higher energy level than the products.
- D.The energy change, ΔH, is positive.
Question 6
2 marks · Normal
Answer and see the solution →The reaction between magnesium and dilute hydrochloric acid is exothermic.
State what you would observe if you held the test tube during this reaction. Explain your answer.
Question 7
4 marks · Normal
Answer and see the solution →The energy profile diagram below represents an endothermic reaction.
Energy profile for an endothermic reaction (a)[2 marks]Label the diagram with:
(i) The activation energy (Ea).
(ii) The enthalpy change (ΔH).
(b)[2 marks]Explain why the reaction shown is endothermic.
Question 8
3 marks · Normal
Answer and see the solution →A student investigates three different reactions in identical test tubes. She measures the temperatures before and after each reaction:
Temperature changes for three reactions Reaction Initial temperature (°C) Final temperature (°C) A 21.0 34.0 B 20.5 15.8 C 22.0 21.7 Which of these reactions is exothermic? Calculate the temperature change for each reaction to justify your answer.