Pearson Edexcel International GCSE (9–1) · CHEMISTRY · Chapter
Reversible Reactions and Equilibria
144 practice questions
Topics covered
- Reversibility and dynamic equilibria19 practice questions
- Reversible reactions in a sealed container18 practice questions
- The position of equilibrium20 practice questions
- Changing the pressure19 practice questions
- Changing the temperature19 practice questions
- Adding a catalyst19 practice questions
- The effect of concentration19 practice questions
Practice questions
141–144 of 144
Question 141
6 marks · Normal
Answer and see the solution →Consider the equilibrium:
(a)[2 marks]State whether the forward reaction is exothermic or endothermic. Give a reason based on the value of ΔH.
(b)[2 marks]Predict and explain what happens to the amount of PCl₃(g) at equilibrium if the temperature is increased.
(c)[2 marks]State whether adding a catalyst affects the amount of PCl₃(g) present at equilibrium. Explain your answer.
Question 142
8 marks · Hard
Answer and see the solution →This question is about an industrial process involving a reversible reaction in a sealed vessel:
At dynamic equilibrium, the concentrations of all four gases remain constant. The process operator wants to maximise the production of C.
(a)[2 marks]State two characteristics of a reaction mixture at dynamic equilibrium. Explain why both these characteristics occur.
(b)[2 marks]The operator increases the concentration of A. Predict and explain how the position of equilibrium will change, and what effect this has on the yield of C.
(c)[2 marks]If the concentration of D is continuously removed from the vessel as it forms, explain (i) how the position of equilibrium will change, and (ii) what will happen to the rate of the forward and reverse reactions immediately after removal.
(d)[2 marks]Suggest one reason, based on the above equilibrium, why controlling concentrations is important in industrial chemical processes.
Question 143
8 marks · Hard
Answer and see the solution →An experiment is set up in a sealed container for the reaction below, which can reach dynamic equilibrium:
The concentrations of all substances are measured over time.
(a)[2 marks]Describe the conditions required for the system to reach dynamic equilibrium. Explain why these conditions are necessary.
(b)[2 marks]The concentration of EF increases while E2 and F2 decrease for some time, then all concentrations level off. Explain what this shows about the rate of the forward and reverse reactions at this point.
(c)[2 marks]If more F2 is added to the system at equilibrium, predict and explain what happens to the concentrations of E2, F2, and EF before the system settles at the new equilibrium.
(d)[2 marks]Explain, in terms of equilibrium, why increasing the concentration of F2 can help industries to increase the yield of EF in this reaction.
Question 144
7 marks · Hard
Answer and see the solution →Consider the industrial reaction below, carried out in a sealed vessel:
This reaction can reach dynamic equilibrium. The mixture initially contains only X.
(a)[2 marks]Describe what happens to the concentration of X as the system approaches equilibrium. Explain your answer.
(b)[2 marks]At equilibrium, more X is added. Predict what will happen to the concentrations of Y and Z and explain your answer in terms of the position of equilibrium.
(c)[1 mark]Suggest one reason why maintaining constant concentrations of products in continuous industrial reactions is important.
(d)[2 marks]Explain, using the idea of equilibrium, what would happen to the rate of the forward and reverse reactions immediately after X is added, until the new equilibrium is reached.