Pearson Edexcel International GCSE (9–1) · CHEMISTRY · Unit
Physical Chemistry
442 practice questions
Topics covered
Practice questions
171–180 of 188 · Normal
Question 171
2 marks · Normal
Answer and see the solution →The equation represents a reversible reaction at equilibrium. State and explain the effect on the position of equilibrium if C(g) is removed as soon as it forms.
Question 172
2 marks · Normal
Answer and see the solution →For the following equilibrium in solution: State what will happen to the position of equilibrium if more ions are added to the mixture. Explain your answer.
Question 173
4 marks · Normal
Answer and see the solution →The following reaction is at equilibrium in a closed container: A chemist adds more C to the equilibrium mixture.
(a)[1 mark]Predict the effect of adding more C on the position of equilibrium. (1)
(b)[2 marks]Explain your answer to part (a). (2)
(c)[1 mark]Suggest one way the chemist could adjust the conditions to increase the yield of D. (1)
Question 174
4 marks · Normal
Answer and see the solution →The table below shows the effect of adding reactant X to a mixture at equilibrium: X + Y \( \rightleftharpoons \) Z. Experiment [X] (mol/dm^3) added Rate of forward reaction Rate of backward reaction [Z] at equilibrium (mol) 1 — fast fast 0.70 2 0.20 faster fast 1.00 Use the data in the table to answer the questions.
(a)[1 mark]What happens to the equilibrium position when X is added? (1)
(b)[1 mark]Describe the changes in the rates of the forward and backward reactions when X is added. (1)
(c)[2 marks]Suggest an explanation for the change in the amount of Z at equilibrium. (2)
Question 175
4 marks · Normal
Answer and see the solution →The equilibrium below is present in a sealed container: A student adds more oxygen, , to the vessel.
(a)[1 mark]State the expected effect on the equilibrium position. (1)
(b)[2 marks]Explain your answer to part (a), using ideas about concentration and Le Chatelier’s principle. (2)
(c)[1 mark]What will happen to the concentration of SO3 at equilibrium? (1)
Question 176
6 marks · Normal
Answer and see the solution →This question is about how both the position of equilibrium and changes in pressure affect reversible reactions involving gases.
(a)[2 marks]For the reaction below in a sealed vessel, is dynamic equilibrium reached? Explain your reasoning.
(b)[2 marks]State why changing the pressure only affects the position of equilibrium in reactions with different numbers of gaseous molecules on each side of the equation.
(c)[2 marks]If the pressure is increased in the vessel containing the equilibrium mixture above, state and explain which direction (left or right) the position of equilibrium will shift.
Question 177
6 marks · Normal
Answer and see the solution →Reversible reactions may respond differently to changes in pressure. Consider the information below for the following questions.
Equilibrium mixture at different conditions Condition Percentage of X Percentage of Y At 1 atm 75 25 At 3 atm 85 15 (a)[2 marks]The equilibrium is: State, with a reason, under which condition the position of equilibrium lies further to the right.
(b)[2 marks]Explain why a change in pressure affects the relative percentages of X and Y in this equilibrium.
(c)[2 marks]Predict and explain in which direction (left or right) the equilibrium will shift if the pressure is decreased.
Question 178
6 marks · Normal
Answer and see the solution →The following equation represents a reversible reaction carried out in a sealed container:
(a)[2 marks]State what would happen to the position of equilibrium if the temperature of the system is increased.
(b)[2 marks]Explain why a catalyst does not change the position of equilibrium in this reaction.
(c)[2 marks]The reaction mixture is left for several hours at a constant temperature and with a catalyst present. Would changing the catalyst affect the final amount of SO₃ present at equilibrium? Explain your answer.
Question 179
6 marks · Normal
Answer and see the solution →Hydrogen iodide is formed in a reversible reaction:
(a)[3 marks]Explain, in terms of exothermic and endothermic reactions, what happens to the position of equilibrium if the temperature is decreased.
(b)[3 marks]Explain why adding a catalyst to the sealed reaction vessel does not change the position of equilibrium.
Question 180
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.