Pearson Edexcel International GCSE (9–1) · CHEMISTRY · Section
How does a catalyst work?
20 practice questions
Practice questions
1–9 of 9 · Normal
Question 1
2 marks · Normal
Answer and see the solution →Explain, with reference to activation energy, how a catalyst affects a reaction profile diagram.
Question 2
4 marks · Normal
Answer and see the solution →The diagram below shows a reaction profile for an exothermic reaction, both with and without a catalyst.
Reaction profile diagram for part (b). (a)[1 mark]Identify which curve on the diagram represents the reaction with a catalyst.
(b)[1 mark]On the diagram, mark with a label 'Ea (with catalyst)' the activation energy for the catalysed reaction.
(c)[1 mark]State what happens to the enthalpy change (ΔH) of the reaction when a catalyst is added.
(d)[1 mark]Explain why the reaction happens faster when a catalyst is used.
Question 3
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 4
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 5
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 6
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 7
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 8
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 9
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.