Pearson Edexcel International GCSE (9–1) · CHEMISTRY · Unit
Physical Chemistry
442 practice questions
Topics covered
Practice questions
161–170 of 188 · Normal
Question 161
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 162
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 163
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 164
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 165
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.
Question 166
4 marks · Normal
Answer and see the solution →Chemists compare the effect of adding a catalyst to two different reversible reactions, P and Q.
Reaction Forward rate without catalyst (mol/dm³/s) Reverse rate without catalyst (mol/dm³/s) P 0.03 0.03 Q 0.07 0.02 (a)[1 mark]For which reaction, P or Q, is equilibrium reached faster after adding a catalyst? Explain your answer.
(b)[1 mark]State whether the position of equilibrium changes for either reaction when a catalyst is added.
(c)[2 marks]Give a reason for your answer to part (b).
Question 167
3 marks · Normal
Answer and see the solution →A reversible reaction is at dynamic equilibrium in a sealed container. The forward reaction is exothermic.
A catalyst is added that increases the rate of both the forward and reverse reactions equally.
Explain, using calculations or reasoning, why adding a catalyst does not change the position of equilibrium for this reaction.
Question 168
3 marks · Normal
Answer and see the solution →Consider the equilibrium: A sealed vessel contains 0.20 mol of X and 0.15 mol of Y at equilibrium. If 0.10 mol of Y is removed from the vessel, predict the change in the amount of X at equilibrium. Explain your answer with a calculation showing the direction of shift.
Question 169
3 marks · Normal
Answer and see the solution →In a laboratory, the following reversible reaction is at equilibrium: Explain, in terms of the effect of concentration, how the equilibrium position can be shifted to increase the amount of R(g) produced. Include why each change has this effect.
Question 170
1 mark · Normal
Answer and check →The reversible reaction is at equilibrium. What is the effect on the position of equilibrium if more N(g) is added?
- A.Shifts to the left to form more M.
- B.Shifts to the right to form more N and O.
- C.No change in the position of equilibrium.
- D.The equilibrium stops.