Pearson Edexcel International GCSE (9–1) · CHEMISTRY · Unit
Physical Chemistry
442 practice questions
Topics covered
Practice questions
171–180 of 183 · Easy
Question 171
1 mark · Easy
Answer and see the solution →The equilibrium below is reached in a closed vessel:
State what happens to the position of equilibrium if some HI(g) is removed.
Question 172
3 marks · Easy
Answer and see the solution →Methanol (3e{CH3OH}) is produced in industry by the following equilibrium:
A technician increases the concentration of hydrogen gas (62e{H2}).
(a)[1 mark]State the effect on the position of equilibrium.
(b)[2 marks]Explain your answer in (a).
Question 173
2 marks · Easy
Answer and see the solution →The reaction below is at equilibrium:
At equilibrium, [Q] is 3.0 mol/dm^3 and [P] is 1.0 mol/dm^3. If 0.5 mol/dm^3 of Q is removed, what will [Q] be after the change is compensated and equilibrium is restored? Assume the system restores [Q] to the original value.
Question 174
5 marks · Easy
Answer and see the solution →This question is about reversibility in chemical reactions, especially in sealed containers.
(a)[2 marks]What is meant by a reversible reaction? State the symbol used to represent a reversible reaction in a chemical equation.
(b)Copper(II) sulfate crystals can lose water when heated and regain it when water is added.
(i)[1 mark]Write a balanced chemical equation using symbols to show the reversible change involving hydrated and anhydrous copper(II) sulfate.
(ii)[2 marks]What does it mean if this reaction occurs in a sealed container?
Question 175
5 marks · Easy
Answer and see the solution →This question is about dynamic equilibrium and how it is achieved in sealed containers.
(a)[2 marks]Explain what is meant by dynamic equilibrium in a reversible reaction.
(b)A chemical reaction is happening in a sealed container.
(i)[1 mark]Describe what happens to the concentrations of reactants and products once dynamic equilibrium is reached.
(ii)[2 marks]State the essential feature of the rates of the forward and reverse reactions at equilibrium in a sealed container.
Question 176
5 marks · Easy
Answer and see the solution →Reversible reactions often behave differently in sealed containers. Use your knowledge to answer the following questions.
(a)[2 marks]State one example of a reversible reaction and write its equation using the proper symbol.
(b)[2 marks]Explain why it is important for a container to be sealed when studying the equilibrium of a reversible reaction.
(c)[1 mark]Describe, with reference to sealed containers, how the forward and reverse reactions compare at dynamic equilibrium.
Question 177
7 marks · Easy
Answer and see the solution →A student investigates the thermal decomposition of ammonium chloride in an open dish and a sealed container.
(a)[2 marks]Explain why changing the pressure has little effect on the rate of the decomposition when ammonium chloride is heated as a solid in an open dish.
(b)[2 marks]Write a balanced chemical equation, using the correct symbol, to show that the thermal decomposition of ammonium chloride is a reversible reaction.
(c)[1 mark]If the experiment is repeated in a sealed container, what substances will be present when equilibrium is reached? Give your answer as a list.
(d)[2 marks]Explain why all these substances are present at equilibrium, even though the reaction appears to have stopped.
Question 178
7 marks · Easy
Answer and see the solution →This question is about catalysts and dynamic equilibrium.
(a)[1 mark]State what is meant by a catalyst.
(b)[2 marks]Describe how you could show that manganese(IV) oxide is a catalyst in the decomposition of hydrogen peroxide.
(c)[2 marks]Define dynamic equilibrium in a reversible reaction.
(d)[2 marks]Explain why the concentrations of reactants and products remain constant at dynamic equilibrium, although both reactions are still occurring.
Question 179
7 marks · Easy
Answer and see the solution →This question is about the interpretation of reaction profile diagrams and the properties of equilibrium.
(a)The diagram below shows an energy profile for a reaction without a catalyst.
Reaction profile diagram for an exothermic reaction (no catalyst). (i)[2 marks]Draw on the diagram a line to show how the profile changes when a catalyst is used. Label the activation energy for the catalysed reaction.
(ii)[1 mark]Explain why the overall enthalpy change (ΔH) for the reaction does not change when a catalyst is used.
(b)[2 marks]In a reversible reaction at equilibrium, the following is observed: the concentrations of reactants and products stay the same, even though both the forward and reverse reactions are occurring. Explain why the concentrations remain unchanged at equilibrium, but the reaction is still said to be 'dynamic'.
(c)[2 marks]A student suggests that adding a catalyst will increase the amount of product at equilibrium. Do you agree? Explain your answer.
Question 180
7 marks · Easy
Answer and see the solution →A student investigates the effect of a possible catalyst on the reversible reaction shown below, carried out in a sealed container:
She wishes to know whether the substance speeds up the reaction, and how changes in pressure affect the amount of SO3 at equilibrium.
(a)[3 marks]Describe a method you would use to show that a substance is a catalyst in this reaction.
(b)[2 marks]Explain what is meant by 'the position of equilibrium' for this reaction.
(c)[2 marks]Predict and explain the effect of increasing pressure on the position of equilibrium of this reaction.