plumiThe equilibrium constant Kc: OCR A‑Level Chemistry A questions
OCR A-Level Chemistry A past-paper questions on 3.2.3.3 The equilibrium constant Kc, 2016–2025, with mark schemes and examiner’s reports where available.
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Q3(a)
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All 19 questions on The equilibrium constant Kc, as a list
- June 2025, Paper 3, Q3(a) (5 marks): Methanol, CH3OH, can be made industrially by the reaction of carbon monoxide, CO, with hydrogen, H2, in the presence of a catalyst. This is a reversible reactio
- June 2025, AS Paper 1, Q23(c) (3 marks): The table shows equilibrium concentrations for Equilibrium 23.1. [SO2(g)] / mol dm–3 [O2(g)] / mol dm–3 [SO3(g)] / mol dm–3 25.0 108 42.0 For Equilibrium 23.1 •
- June 2024, AS Paper 1, Q13 (1 mark): The reversible reaction below is at equilibrium. 2SO2(g) + O2(g) 2SO3(g) What is the expression for Kc? [SO2(g)]2 [O2(g)] A [SO3(g)]2 [SO3(g)]2 B [SO2(g)]2 [O2(
- June 2023, AS Paper 1, Q24(a) (1 mark): Why is Equilibrium 24.1 a homogeneous equilibrium? [1]
- June 2023, AS Paper 1, Q24(c)(i) (2 marks): Write the expression for Kc and calculate the numerical value for Kc in Equilibrium 24.1 at this constant temperature. Give your answer to an appropriate number
- June 2022, AS Paper 1, Q13 (1 mark): Four equilibrium reactions are set up. The concentration of each gas in the equilibrium mixtures is 0.1 mol dm–3. Which equilibrium has a numerical Kc value of
- June 2022, AS Paper 2, Q4(a)(ii) (2 marks): A chemist mixes CH4(g) and H2O(g) and leaves the mixture to reach equilibrium. CO(g) + 3H2(g) ΔH = +206 kJ mol–1 CH4(g) + H2O(g) Equilibrium 4.1 The equilibrium
- November 2021, AS Paper 2, Q5(a) (1 mark): Write the expression for the equilibrium constant, Kc, for this equilibrium. [1]
- November 2021, AS Paper 2, Q5(b)(i) (2 marks): Calculate the equilibrium concentration of CH3OH(g). concentration = mol dm–3 [2]
- November 2021, AS Paper 2, Q5(b)(ii) (1 mark): What does the numerical value of Kc tell you about the position of equilibrium? [1]
- November 2020, AS Paper 1, Q13 (1 mark): The reversible reaction below is in equilibrium. 2SO2(g) + O2(g) 2SO3(g) The equilibrium concentrations are shown in the table. Substance SO2(g) O2(g) SO3(g) Eq
- November 2020, AS Paper 2, Q4(b)(i) (1 mark): Write the expression for the equilibrium constant, Kc, for this equilibrium. [1]
- November 2020, AS Paper 2, Q4(b)(ii) (1 mark): In the equilibrium mixture at 400 °C, the equilibrium concentration of Cl 2(g) is found to be 0.17 mol dm−3. The student calculates that the equilibrium concent
- November 2020, AS Paper 2, Q4(b)(iii) (2 marks): At 400 °C, Kc = 0.015 moldm–3. Calculate the equilibrium concentration of NOCl (g) at 400 °C. equilibrium concentration of NOCl (g) = mol dm−3 [2]
- June 2019, AS Paper 1, Q24(a)(ii) (2 marks): Using certain conditions, equilibrium 24.1 has the equilibrium concentrations in the table. Equilibrium concentration Substance / mol dm−3 N2(g) 1.25 H2(g) 2.75
- June 2018, AS Paper 1, Q14 (1 mark): The reversible reaction below is at equilibrium. N2(g) + 3H2(g) 2NH3(g) What is the expression for Kc? [N2(g)] [H2(g)]3 A [NH3(g)]2 [NH3(g)]2 B [N2(g)] [H2(g)]3
- June 2018, AS Paper 2, Q4(b) (1 mark): Write an expression for the equilibrium constant, Kc, in equilibrium 4.1. [1]
- June 2017, AS Paper 1, Q23(c) (2 marks): A chemist investigates the equilibrium that produces methanol: CO(g) + 2H2(g) CH3OH(g) The chemist mixes CO(g) with H2(g) and leaves the mixture to react until
- June 2016, AS Paper 1, Q25(b) (4 marks): Under certain conditions, Kc for equilibrium 25.1 is 0.160 dm3 mol–1. The equilibrium mixture under these conditions has the following concentrations of SO2 and
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