Pearson Edexcel International GCSE (9–1) · CHEMISTRY · Chapter
Rates of Reaction
164 practice questions
Topics covered
- Experiments to measure the rate of reaction19 practice questions
- Explaining what's happening19 practice questions
- Changing the surface area of the reactants19 practice questions
- Changing the concentration of the reactants19 practice questions
- Changing the pressure on the reaction19 practice questions
- What are catalysts?19 practice questions
- How does a catalyst work?20 practice questions
- Catalysts in industry19 practice questions
Practice questions
21–27 of 27 · Hard
Question 21
2 marks · Hard
Answer and see the solution →A student says that using a catalyst lowers the energy of the reactants in a chemical reaction. Evaluate this statement. Use ideas from reaction profile diagrams in your answer.
Question 22
5 marks · Hard
Answer and see the solution →The diagram below shows the energy changes during a chemical reaction.
(a)[2 marks]Explain, in terms of activation energy, how a catalyst increases the rate of a reaction.
(b)[2 marks]A student suggests that adding a catalyst would change the total enthalpy change (ΔH) of a reaction. Is this correct? Explain your answer.
(c)[1 mark]Describe, using a reaction profile diagram, what happens to the activation energy and enthalpy change of a reaction when a catalyst is used.
Question 23
2 marks · Hard
Answer and see the solution →Describe two key features that should be shown on a reaction profile diagram to illustrate the effect of a catalyst on a reaction.
Question 24
2 marks · Hard
Answer and see the solution →Ammonia is produced in the Haber process, which requires high temperatures and pressures. The process uses an iron catalyst.
Explain two ways that using a catalyst in the Haber process is important for the chemical industry.
Question 25
7 marks · Hard
Answer and see the solution →A laboratory chemist is investigating two gas-phase reactions: the catalytic decomposition of hydrogen peroxide, and the reaction of nitrogen and hydrogen to make ammonia. She explores how changes in pressure and the use of catalysts can affect the rate of these reactions.
(a)[2 marks]Explain how increasing the pressure affects the rate of both these gas-phase reactions. Give a reason for your answer.
(b)[2 marks]Describe the role of a catalyst in the decomposition of hydrogen peroxide. Name a catalyst commonly used for this reaction.
(c)[3 marks]The chemist doubles the pressure in the reaction vessel for the decomposition of hydrogen peroxide (in the gas phase) while also adding a catalyst. Predict and explain how the combined changes will affect the rate of reaction, compared to the original conditions.
Question 26
7 marks · Hard
Answer and see the solution →Some students investigate the effect of pressure on the rate of the reaction between two liquids. They then study the catalytic decomposition of a liquid, hydrogen peroxide.
(a)[2 marks]Explain, with a reason, why increasing the pressure has little effect on the rate of reaction between only liquids or only solids.
(b)[1 mark]State what is meant by the term 'catalyst'.
(c)[2 marks]In an experiment, a student adds manganese(IV) oxide to hydrogen peroxide solution and quickly fits a bung and gas syringe. The apparatus is shown below.
Apparatus for measuring the volume of oxygen produced during the decomposition of hydrogen peroxide. Describe how the student could show that manganese(IV) oxide is a true catalyst in this reaction.
(d)[2 marks]Explain why increasing the pressure would not speed up the same hydrogen peroxide decomposition experiment if all the reactants were liquid.
Question 27
7 marks · Hard
Answer and see the solution →A researcher investigates the decomposition of hydrogen peroxide to oxygen gas. She runs two versions of the experiment: one at low pressure without a catalyst, the other at high pressure with a catalyst.
(a)[1 mark]Describe what is meant by the term 'catalyst'.
(b)[2 marks]Explain how increasing the pressure affects the rate of the decomposition of hydrogen peroxide when both hydrogen peroxide and oxygen are in the gas phase.
(c)[4 marks]The table gives the results for two versions of the reaction:
Experiment Pressure Catalyst Time to collect 20 cm³ O₂ / s 1 low none 120 2 high manganese(IV) oxide 20 Compare the time taken to collect the same volume of oxygen in the two experiments. Explain your answer in terms of the effects of both pressure and the catalyst.