Pearson Edexcel International GCSE (9–1) · CHEMISTRY · Unit
Physical Chemistry
442 practice questions
Topics covered
Practice questions
381–390 of 442
Question 381
3 marks · Easy
Answer and see the solution →The concentrations of reactants and products in a reversible reaction at equilibrium are measured every minute. At minute 4, a catalyst is added. The concentrations at each minute are shown below.
Concentration data (mol/dm³) Time (min) [Reactant] [Product] 0 1.00 0.00 1 0.85 0.15 2 0.75 0.25 3 0.71 0.29 4 0.70 0.30 5 0.70 0.30 6 0.70 0.30 (a)[1 mark]Describe the effect of adding the catalyst on the time taken to reach equilibrium.
(b)[1 mark]Use the data to state the concentrations at equilibrium.
(c)[1 mark]Does adding the catalyst change the equilibrium concentrations? Explain your answer.
Question 382
1 mark · Easy
Answer and see the solution →What does a catalyst do to the rates of the forward and reverse reactions in a reversible process?
Question 383
3 marks · Easy
Answer and see the solution →Nitrogen dioxide, NO₂, and dinitrogen tetroxide, N₂O₄, form a reversible reaction at equilibrium:
(a)[1 mark]State what happens to the colour of the mixture when a catalyst is added.
(b)[1 mark]Explain whether the ratio of NO₂ to N₂O₄ changes after the catalyst is added.
(c)[1 mark]Give a reason for your answer to (b).
Question 384
2 marks · Easy
Answer and see the solution →A reversible reaction reaches equilibrium after 12 minutes. When a catalyst is added, it reaches equilibrium in just 3 minutes. Calculate by what factor the rate of reaching equilibrium has increased. State if the position of equilibrium is affected.
Question 385
2 marks · Normal
Answer and see the solution →Explain why adding a catalyst does not change the position of equilibrium in a reversible reaction.
Question 386
4 marks · Normal
Answer and see the solution →The decomposition of hydrogen peroxide is a reversible reaction represented by the following equation:
(a)[1 mark]State what effect, if any, adding a catalyst will have on the rates of the forward and reverse reactions.
(b)[1 mark]Explain how the catalyst affects the time taken to reach equilibrium.
(c)[2 marks]Does adding a catalyst change the position of equilibrium for this reaction? Explain your answer.
Question 387
3 marks · Normal
Answer and see the solution →A teacher tells her class that adding a catalyst to a reversible reaction will make the equilibrium mixture contain more products. Is she correct? Explain your reasoning.
Question 388
4 marks · Normal
Answer and see the solution →The graph below shows the concentration of reactant A and product B in a reversible reaction over time.
Concentrations vs time for a reversible reaction. At t = 5 min, a catalyst is added. (a)[1 mark]What evidence from the graph shows that the reaction has reached equilibrium?
(b)[2 marks]Describe what happens to the concentrations of A and B immediately after the catalyst is added at t = 5 min.
(c)[1 mark]Explain why the equilibrium concentrations do not change after the catalyst is added.
Question 389
1 mark · Normal
Answer and check →What is the correct effect of a catalyst on a reversible chemical reaction at equilibrium?
- A.It shifts the equilibrium towards the products.
- B.It has no effect on the position of equilibrium.
- C.It increases the amount of reactants at equilibrium.
- D.It stops the reverse reaction.
Question 390
2 marks · Normal
Answer and see the solution →State two reasons why adding a catalyst is useful in reversible reactions even though it does not affect the position of equilibrium.