plumiEquilibrium constants, ∆Stotal and extent of reaction: Edexcel International A Level Chemistry questions
Edexcel International A Level Chemistry past-paper questions on 13.1.3 Equilibrium constants, ∆Stotal and extent of reaction, 2019–2025, with mark schemes and examiner’s reports where available.
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Q13(c)
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All 17 questions on Equilibrium constants, ∆Stotal and extent of reaction, as a list
- June 2025, Unit 4, Q13(c) (1 mark): What is the relationship between the equilibrium constant, K, and ΔStotal ? (1) A ΔStotal = R ln K ln ΔStotal = R K B C ΔStotal = R log K D log ΔStotal = R K
- June 2024, Unit 4, Q5 (1 mark): For all chemical reactions, the equilibrium constant, K, is related to the total entropy change, ΔStotal , by the expression shown. ΔStotal = R ln K ΔStotal for
- January 2024, Unit 4, Q19(a)(iii) (3 marks): Deduce the effect of increasing the temperature on the total entropy change of this reaction, ΔStotal, and on the value of the equilibrium constant, Kc. Assume
- June 2023, Unit 4, Q18(b) (2 marks): The equilibrium constant, Kp , for the reaction at 298 K is 1.55 × 106 atm–½. State what this value of the equilibrium constant indicates about the position of
- October 2022, Unit 4, Q18(c)(i) (2 marks): Complete the table of data. (2)
- October 2022, Unit 4, Q18(c)(ii) (3 marks): Plot a graph of ln Kc against 1 / T. Include a line of best fit. (3) ln Kc 1 / T (K–1)
- October 2022, Unit 4, Q18(c)(iii) (1 mark): Determine the gradient of your graph. You must show your working on the graph. (1)
- October 2022, Unit 4, Q18(c)(iv) (2 marks): The gradient of the graph from (c)(iii) is related to the enthalpy change of the reaction, ∆H . gradient = Δ H − R Calculate ∆H , in J mol−1 , using your value
- October 2022, Unit 4, Q18(c)(v) (2 marks): The free energy change for the reaction, ∆G , is related to entropy and can be calculated from Kc . ∆G = −RT ln Kc Calculate ∆G at 620 K , using this equation a
- January 2022, Unit 4, Q22(d)(i) (1 mark): State the relationship between the total entropy, ΔS total, and the equilibrium constant, K. (1)
- January 2022, Unit 4, Q22(d)(ii) (2 marks): Calculate the value of the equilibrium constant K at 750 K. [ΔS total at 750 K = –37.7 J K–1 mol–1] (2)
- January 2022, Unit 4, Q22(d)(iii) (3 marks): Explain why ΔS total decreases with an increase in temperature. (3)
- June 2021, Unit 4, Q20(b)(iv) (2 marks): Use your answer to (b)(iii) to calculate a value for the total entropy change of the reaction, ΔStotal . (2)
- January 2021, Unit 4, Q6 (1 mark): The total entropy change, ¨Stotal , of a reaction at 298 K is −85.0 J K−1 mol−1. What is the value of the equilibrium constant for this reaction at 298 K? [R =
- October 2020, Unit 4, Q19(a)(v) (6 marks): Explain one advantage and one disadvantage of using a temperature higher than 700 K in the Haber process. Consider the effect of an increase in temperature on t
- January 2020, Unit 4, Q8 (1 mark): Equal amounts of W and X are mixed and allowed to reach equilibrium. W + X U Y + Z The value of the equilibrium constant is Kc = 4.85. At equilibrium, the mixtu
- January 2020, Unit 4, Q19(a)(iii) (2 marks): Use your answer from (a)(i) to calculate the equilibrium constant for the reaction at 298 K. (2)
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