Pearson Edexcel International GCSE (9–1) · CHEMISTRY · Unit
Physical Chemistry
442 practice questions
Topics covered
Practice questions
391–400 of 442
Question 391
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 392
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 393
2 marks · Hard
Answer and see the solution →A chemist adds a catalyst to a reversible reaction mixture at equilibrium. The student expects the concentration of products to increase once the catalyst is added.
Explain, with a reason, whether the student's expectation is correct.
Question 394
5 marks · Hard
Answer and see the solution →A student investigates the following reversible reaction at equilibrium: \[ \ce{CO(g) + H2O(g) \rightleftharpoons CO2(g) + H2(g)} \] The student adds a catalyst to the closed reaction vessel.
(a)State what happens to: (i) the rate at which equilibrium is reached (ii) the position of equilibrium after the catalyst is added.
(i)[1 mark]the rate at which equilibrium is reached
(ii)[1 mark]the position of equilibrium
(b)[3 marks]Explain, with reasons, why a catalyst does or does not affect the position of equilibrium in a reversible reaction. Include reference to the rates of the forward and reverse reactions in your answer.
Question 395
2 marks · Hard
Answer and see the solution →Explain why the addition of a catalyst does not affect the position of equilibrium in a reversible reaction.
Question 396
1 mark · Easy
Answer and see the solution →For the following equilibrium in solution:
State what will happen to the position of equilibrium if more B is added to the mixture.
Question 397
3 marks · Easy
Answer and see the solution →The following reversible reaction is at equilibrium in a closed container:
A chemist removes some G(g) from the equilibrium mixture.
(a)[1 mark]State how the position of equilibrium will change.
(b)[1 mark]Give a reason for your answer in (a).
(c)[1 mark]Name the principle that explains your answer.
Question 398
2 marks · Easy
Answer and see the solution →A system is at equilibrium with the following reaction:
At equilibrium, the concentration of Z is 4.0 mol/dm^3. If 2.0 mol/dm^3 of Z is suddenly removed, how many moles per dm^3 of Z will form to restore equilibrium? Assume all change is due to the forward reaction.
Question 399
2 marks · Easy
Answer and see the solution →The following reaction is at equilibrium in a sealed container:
Explain, in terms of concentration, what will happen to the position of equilibrium if extra KL(g) is added.
Question 400
3 marks · Easy
Answer and see the solution →The equilibrium below is set up in a sealed vessel:
The graph shows how the concentration of AB(g) changes after some B2(g) is added:
Concentration of AB(g) vs. time after B2(g) is added. (a)[1 mark]Describe what happens to [AB] after B2(g) is added.
(b)[2 marks]Predict and explain the direction in which the position of equilibrium shifts after B2(g) is added.