Pearson Edexcel International GCSE (9–1) · CHEMISTRY · Section
How does a catalyst work?
20 practice questions
Practice questions
11–20 of 20
Question 11
3 marks · Normal
Answer and see the solution →A reaction without a catalyst has an activation energy of 180 kJ/mol. When a catalyst is added, the activation energy decreases to 100 kJ/mol.
Calculate the difference in activation energy as a result of adding the catalyst.
Explain what this change means for the number of successful collisions.
Question 12
3 marks · Normal
Answer and see the solution →A student claims, "A catalyst lowers the energy of the reactants."
Discuss whether this statement is correct, using ideas from reaction profile diagrams and activation energy.
Question 13
2 marks · Normal
Answer and see the solution →State what a reaction profile diagram shows about the effect of a catalyst on: (i) the activation energy (ii) the overall energy change (enthalpy change, ).
Question 14
4 marks · Normal
Answer and see the solution →(a)[2 marks]The diagram below shows the reaction profile for a chemical reaction without a catalyst.
Reaction profile diagram for a reaction without a catalyst. Draw on the diagram, using a dashed curve, how the reaction profile would look if a catalyst was used.
(b)[2 marks]Explain, using the diagram, how the catalyst affects the reaction.
Question 15
3 marks · Normal
Answer and see the solution →A reaction has reactants at an energy level of 95 kJ/mol, a peak (without a catalyst) at 155 kJ/mol, and products at 65 kJ/mol.
A catalyst provides an alternative pathway with a peak at 110 kJ/mol.
Calculate:
(a)[1 mark]The activation energy without a catalyst.
(b)[1 mark]The activation energy with a catalyst.
(c)[1 mark]The difference in activation energy caused by the catalyst.
Question 16
3 marks · Normal
Answer and see the solution →A student says: 'When you add a catalyst, more particles in the reaction mixture have the required activation energy to react.'
Explain, with reference to reaction profile diagrams, whether this statement is correct.
Question 17
4 marks · Normal
Answer and see the solution →The table shows energy values for a chemical reaction.
Description Energy (kJ/mol) Reactants 75 Peak without catalyst 142 Peak with catalyst 95 Products 45 (a)[1 mark]Calculate the activation energy for the uncatalysed reaction.
(b)[1 mark]Calculate the activation energy for the catalysed reaction.
(c)[1 mark]Calculate the overall energy change () for the reaction.
(d)[1 mark]State how the catalyst changes the reaction profile diagram.
Question 18
2 marks · Hard
Answer and see the solution →The diagram below shows a reaction profile for an exothermic reaction. The activation energy for the uncatalysed reaction is much larger than for the catalysed reaction.
Reaction profile for an exothermic reaction (uncatalysed and catalysed). Describe what the dashed line on this diagram represents. Explain how a catalyst causes this change.
Question 19
5 marks · Hard
Answer and see the solution →A student draws the following reaction profile diagram for a certain chemical reaction:
Reaction profile for a chemical reaction. Use the diagram to answer the questions below.
(a)[1 mark]State the term used for the energy difference from the reactants up to the peak without a catalyst.
(b)[2 marks]Describe how the diagram shows the effect of a catalyst on the reaction.
(c)[2 marks]Explain why many more particles in the reaction mixture can react when a catalyst is used, referring to the activation energy.
Question 20
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.