Pearson Edexcel International GCSE (9–1) · CHEMISTRY · Unit
Physical Chemistry
442 practice questions
Topics covered
Practice questions
111–120 of 183 · Easy
Question 111
3 marks · Easy
Answer and see the solution →The contact process for making sulfuric acid uses vanadium(V) oxide as a catalyst. In one experiment, 100 cm³ of sulfur dioxide and excess oxygen were reacted at 450°C and 2 atm, both with and without the catalyst. With the catalyst, the reaction reached equilibrium in 2 minutes. Without the catalyst, it took 10 minutes.
(a)[1 mark]How does the catalyst affect the rate of the reaction?
(b)[1 mark]Does the catalyst increase the amount of sulfuric acid produced at equilibrium? Give a reason for your answer.
(c)[1 mark]Explain why using a catalyst is economically important in this reaction.
Question 112
1 mark · Easy
Answer and see the solution →State how a catalyst affects the activation energy of a reaction.
Question 113
3 marks · Easy
Answer and see the solution →(a)[3 marks]Draw a fully labelled reaction profile diagram for a reaction that is exothermic, showing the effect of a catalyst.
Question 114
2 marks · Easy
Answer and see the solution →In an experiment, two reactions are compared: one with a catalyst and one without. The time for the reaction without a catalyst is 30 minutes. With a catalyst, the same reaction takes 10 minutes. If a student wants to show the substance is a catalyst, what further step should she take besides measuring the rates? Explain your answer.
Question 115
2 marks · Easy
Answer and see the solution →Draw a reaction profile diagram for a reaction. Your diagram should show both the activation energy for the uncatalysed and catalysed reaction paths. Clearly label the energy of reactants, energy of products, activation energy for both paths, and the effect of the catalyst.
Question 116
5 marks · Easy
Answer and see the solution →Some students investigate how quickly a metal carbonate reacts with dilute acid. They want to investigate the effect of changing the surface area of the solid on the rate of reaction.
(a)[2 marks]Describe how the students could carry out an experiment to investigate the effect of surface area on the rate of reaction between calcium carbonate and dilute hydrochloric acid.
(b)[1 mark]State one way the results from this experiment could be measured.
(c)[2 marks]Explain, using collision theory, why smaller pieces of calcium carbonate react faster than large pieces when added to hydrochloric acid.
Question 117
5 marks · Easy
Answer and see the solution →The diagram below shows apparatus used to measure the rate of a reaction between marble chips (calcium carbonate) and dilute hydrochloric acid.
Apparatus for measuring mass loss. (a)[1 mark]State what happens to the mass reading as the reaction occurs.
(b)[1 mark]Suggest why a cotton wool plug is placed in the neck of the flask.
(c)[2 marks]Describe two different ways to increase the rate of this reaction.
(d)[1 mark]Explain, using collision theory, why increasing the temperature increases the rate of reaction.
Question 118
5 marks · Easy
Answer and see the solution →A student carries out an experiment to measure how quickly hydrogen peroxide decomposes using a catalyst. The volume of oxygen gas collected every 30 seconds is shown on a graph: the curve is steep at first, then becomes less steep and finally flat.
(a)[1 mark]State one piece of apparatus the student could use to collect the oxygen gas.
(b)[1 mark]Describe how using a different catalyst could help the student measure the effect of catalysts on the rate.
(c)[1 mark]State what happens to the rate of reaction as shown by the graph.
(d)[2 marks]Explain why the rate of reaction changes in this way, using ideas from collision theory.
Question 119
5 marks · Easy
Answer and see the solution →A student investigates the rate of reaction between excess marble chips (calcium carbonate) and dilute hydrochloric acid in a flask. The CO produced escapes, causing the total mass to decrease. The student records the following results:
Data for the reaction Time (min) Mass lost (g) 0 0.00 1 0.52 2 0.81 3 0.95 (a)[2 marks]Calculate the average rate of reaction in g/min during the first 2 minutes. Show your working.
(b)[3 marks]Use collision theory to explain why the rate of reaction changes after the first 2 minutes. Refer to the results from part (a) in your answer.
Question 120
1 mark · Easy
Answer and see the solution →State one characteristic of a system at dynamic equilibrium.