Pearson Edexcel International GCSE (9–1) · CHEMISTRY · Unit
Physical Chemistry
442 practice questions
Topics covered
Practice questions
41–50 of 71 · Hard
Question 41
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 42
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 43
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 44
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 45
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.
Question 46
2 marks · Hard
Answer and see the solution →Explain, in terms of particle behaviour, why the concentrations of reactants and products remain constant in a sealed container when a reversible reaction has reached dynamic equilibrium.
Question 47
5 marks · Hard
Answer and see the solution →A reversible reaction between gases takes place in a sealed container.
(a)[2 marks]State two characteristics of the system when it has reached dynamic equilibrium.
(b)[3 marks]Explain what would happen to the amount of if the pressure on the system is increased, and relate your answer to the number of moles of gas on each side of the equation.
Question 48
2 marks · Hard
Answer and see the solution →Write a balanced symbol equation for the reversible thermal decomposition of ammonium chloride, including the correct symbol for a reversible reaction.
Question 49
2 marks · Hard
Answer and see the solution →State two essential features that define a sealed container in the context of reversible reactions.
Question 50
5 marks · Hard
Answer and see the solution →(a)[2 marks]Explain what happens to the forward and backward reaction rates when a reversible reaction first starts in a sealed container.
(b)[2 marks]Describe what is meant by equilibrium in this context.
(c)[1 mark]State one reason why equilibrium can only be reached if the container is sealed.