Skip to content
Try on iPad

How far?: OCR A‑Level Chemistry A questions

Every OCR A-Level Chemistry A exam question on 5.1.2 How far?, 2016–2025, with its mark scheme and examiner’s report.

Find questions1,820
Calculations

1,820 questions

  1. Q17(c)(i)

    June 2025 · Paper 1

    1 mark5.1.2 How far?
    The whole paper ↗
    June 2025 Paper 1, question 17(c)(i): Explain why Kp for Equilibrium 17.3 has no units. [1]

  2. Q17(c)(ii)

    June 2025 · Paper 1

    3 marks5.1.2 How far?
    The whole paper ↗
    June 2025 Paper 1, question 17(c)(ii): An equal number of moles of steam and carbon monoxide are left at 700 K in a sealed container until equilibrium is reached. At equilibrium, both H2 and CO2 have

  3. Q17(c)(iii)

    June 2025 · Paper 1

    2 marks5.1.2 How far?
    The whole paper ↗
    June 2025 Paper 1, question 17(c)(iii): At a second temperature the value of Kp for Equilibrium 17.3 is 129. Explain whether the second temperature is higher or lower than 700 K. [2]

  4. Q3(a)

    June 2025 · Paper 3

    5 marks3.2.3 Chemical equilibrium5.1.2 How far?
    The whole paper ↗
    June 2025 Paper 3, question 3(a): 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

  5. Q18(a)(i)

    June 2024 · Paper 1

    5 marks5.1.2 How far?
    The whole paper ↗
    June 2024 Paper 1, question 18(a)(i): 2.25 moles of SO3 is heated to 550 °C in the presence of a catalyst and the resulting mixture allowed to reach equilibrium. The equilibrium mixture contains 0.9

  6. Q18(a)(ii)

    June 2024 · Paper 1

    2 marks5.1.2 How far?
    The whole paper ↗
    June 2024 Paper 1, question 18(a)(ii): The numerical values of Kp for Equilibrium 18.1 at temperatures T1 and T2 are shown below. Temperature Kp 3.3 × 10–5 T1 7.7 × 10–2 T2 Explain why T2 is a higher

  7. Q18(a)(iii)

    June 2024 · Paper 1

    2 marks5.1.2 How far?
    The whole paper ↗
    June 2024 Paper 1, question 18(a)(iii): Suggest how the value of Kp would change if the reaction was repeated with no catalyst added and the pressure of the system increased. Tick (✓) one box in each

  8. Q19(a)(i)

    June 2023 · Paper 1

    5 marks5.1.2 How far?
    The whole paper ↗
    June 2023 Paper 1, question 19(a)(i): A sealed flask containing 6.00 moles of NO2(g) is heated to a constant temperature and allowed to reach equilibrium. The equilibrium mixture contains 5.40 mol o

  9. Q19(a)(ii)

    June 2023 · Paper 1

    3 marks5.1.2 How far?
    The whole paper ↗
    June 2023 Paper 1, question 19(a)(ii): The sealed flask in (a)(i) is then heated to a higher temperature at an increased pressure. The system is allowed to reach equilibrium again. Explain why it is

  10. Q6(d)

    June 2023 · Paper 3

    5 marks5.1.2 How far?
    The whole paper ↗
    June 2023 Paper 3, question 6(d): In the UK, most sulfuric acid, H2SO4, is manufactured by the Contact process. One stage in the Contact process involves the equilibrium between sulfur dioxide,

  11. Q20(a)

    June 2022 · Paper 1

    6 marks5.1.2 How far?
    The whole paper ↗
    June 2022 Paper 1, question 20(a): This question is about equilibria involving hydrogen. (a)* Hydrogen is used industrially to manufacture ammonia. The equilibrium is shown below. 2NH3(g) ∆H = –9

  12. Q20(b)(i)

    June 2022 · Paper 1

    1 mark5.1.2 How far?
    The whole paper ↗
    June 2022 Paper 1, question 20(b)(i): When the temperature is decreased, the value of Kp decreases. Determine whether the forward reaction is exothermic or endothermic. Explain your answer. [1]

  13. Q20(b)(ii)

    June 2022 · Paper 1

    1 mark5.1.2 How far?
    The whole paper ↗
    June 2022 Paper 1, question 20(b)(ii): Two students are discussing the effect of pressure on the equilibrium position of Equilibrium 20.2. Student 1 says: “There are more moles of products than react

  14. Q20(c)(i)

    November 2021 · Paper 1

    4 marks5.1.2 How far?
    The whole paper ↗
    November 2021 Paper 1, question 20(c)(i): Calculate Kp, in MPa–1, for Equilibrium 20.1. Give your answer to 3 significant figures. Kp = MPa–1 [4]

  15. Q20(c)(ii)

    November 2021 · Paper 1

    3 marks5.1.2 How far?
    The whole paper ↗
    November 2021 Paper 1, question 20(c)(ii): The chemist then repeats the experiment three times. In each experiment, the chemist makes one change but uses the same initial amounts of NO and O2. Complete t

  16. Q1(a)

    November 2021 · Paper 3

    2 marks5.1.2 How far?
    The whole paper ↗
    November 2021 Paper 3, question 1(a): A flask contains 110 g CO2 and 120 g O2 at a pressure of 50.0 atm. What is the partial pressure of the CO2? partial pressure of CO2 = atm [2]

  17. Q1(b)

    November 2021 · Paper 3

    2 marks5.1.2 How far?
    The whole paper ↗
    November 2021 Paper 3, question 1(b): Pure PCl5 is placed in a sealed container which is heated to 200 ºC. An equilibrium is set up: PCl5(g) PCl3(g) + Cl2(g) Under these conditions: Kc = 8.00 × 10–3

  18. Q9

    November 2020 · Paper 1

    1 mark5.1.2 How far?
    The whole paper ↗
    November 2020 Paper 1, question 9: The reversible reaction of nitrogen and hydrogen to form ammonia is shown below. N2(g) + 3H2(g) 2NH3(g) In the equilibrium mixture, the partial pressure of N2 i

  19. Q20(b)

    November 2020 · Paper 1

    4 marks5.1.2 How far?
    The whole paper ↗
    November 2020 Paper 1, question 20(b): The student carries out a second experiment to determine the value of Kc for this reaction. The student mixes 9.6 g of CH3OH with 12.0 g of CH3COOH and adds the

  20. Q5(a)

    November 2020 · Paper 3

    2 marks5.1.2 How far?5.2.2 Enthalpy and entropy
    The whole paper ↗
    November 2020 Paper 3, question 5(a): The table shows the values of Kp at different temperatures for an equilibrium. Complete the table by adding the missing values of 1 T and ln Kp. Temperature, T
All 41 questions on How far?, as a list
  1. June 2025, Paper 1, Q17(c)(i) (1 mark): Explain why Kp for Equilibrium 17.3 has no units. [1]
  2. June 2025, Paper 1, Q17(c)(ii) (3 marks): An equal number of moles of steam and carbon monoxide are left at 700 K in a sealed container until equilibrium is reached. At equilibrium, both H2 and CO2 have
  3. June 2025, Paper 1, Q17(c)(iii) (2 marks): At a second temperature the value of Kp for Equilibrium 17.3 is 129. Explain whether the second temperature is higher or lower than 700 K. [2]
  4. 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
  5. June 2024, Paper 1, Q18(a)(i) (5 marks): 2.25 moles of SO3 is heated to 550 °C in the presence of a catalyst and the resulting mixture allowed to reach equilibrium. The equilibrium mixture contains 0.9
  6. June 2024, Paper 1, Q18(a)(ii) (2 marks): The numerical values of Kp for Equilibrium 18.1 at temperatures T1 and T2 are shown below. Temperature Kp 3.3 × 10–5 T1 7.7 × 10–2 T2 Explain why T2 is a higher
  7. June 2024, Paper 1, Q18(a)(iii) (2 marks): Suggest how the value of Kp would change if the reaction was repeated with no catalyst added and the pressure of the system increased. Tick (✓) one box in each
  8. June 2023, Paper 1, Q19(a)(i) (5 marks): A sealed flask containing 6.00 moles of NO2(g) is heated to a constant temperature and allowed to reach equilibrium. The equilibrium mixture contains 5.40 mol o
  9. June 2023, Paper 1, Q19(a)(ii) (3 marks): The sealed flask in (a)(i) is then heated to a higher temperature at an increased pressure. The system is allowed to reach equilibrium again. Explain why it is
  10. June 2023, Paper 3, Q6(d) (5 marks): In the UK, most sulfuric acid, H2SO4, is manufactured by the Contact process. One stage in the Contact process involves the equilibrium between sulfur dioxide,
  11. June 2022, Paper 1, Q20(a) (6 marks): This question is about equilibria involving hydrogen. (a)* Hydrogen is used industrially to manufacture ammonia. The equilibrium is shown below. 2NH3(g) ∆H = –9
  12. June 2022, Paper 1, Q20(b)(i) (1 mark): When the temperature is decreased, the value of Kp decreases. Determine whether the forward reaction is exothermic or endothermic. Explain your answer. [1]
  13. June 2022, Paper 1, Q20(b)(ii) (1 mark): Two students are discussing the effect of pressure on the equilibrium position of Equilibrium 20.2. Student 1 says: “There are more moles of products than react
  14. November 2021, Paper 1, Q20(c)(i) (4 marks): Calculate Kp, in MPa–1, for Equilibrium 20.1. Give your answer to 3 significant figures. Kp = MPa–1 [4]
  15. November 2021, Paper 1, Q20(c)(ii) (3 marks): The chemist then repeats the experiment three times. In each experiment, the chemist makes one change but uses the same initial amounts of NO and O2. Complete t
  16. November 2021, Paper 3, Q1(a) (2 marks): A flask contains 110 g CO2 and 120 g O2 at a pressure of 50.0 atm. What is the partial pressure of the CO2? partial pressure of CO2 = atm [2]
  17. November 2021, Paper 3, Q1(b) (2 marks): Pure PCl5 is placed in a sealed container which is heated to 200 ºC. An equilibrium is set up: PCl5(g) PCl3(g) + Cl2(g) Under these conditions: Kc = 8.00 × 10–3
  18. November 2020, Paper 1, Q9 (1 mark): The reversible reaction of nitrogen and hydrogen to form ammonia is shown below. N2(g) + 3H2(g) 2NH3(g) In the equilibrium mixture, the partial pressure of N2 i
  19. November 2020, Paper 1, Q20(b) (4 marks): The student carries out a second experiment to determine the value of Kc for this reaction. The student mixes 9.6 g of CH3OH with 12.0 g of CH3COOH and adds the
  20. November 2020, Paper 3, Q5(a) (2 marks): The table shows the values of Kp at different temperatures for an equilibrium. Complete the table by adding the missing values of 1 T and ln Kp. Temperature, T
  21. November 2020, Paper 3, Q5(b) (1 mark): State and explain how increasing the temperature affects the position of this equilibrium and whether the forward reaction is exothermic or endothermic. [1]
  22. November 2020, Paper 3, Q5(c) (4 marks): Plot a graph of ln Kp against 1 T using the axes provided on the opposite page. Use your graph and equation 5.1 to determine ∆H, in kJ mol−1, for this equilibri
  23. June 2019, Paper 1, Q19(b)(i) (2 marks): Write an expression for Kp for Equilibrium 1. Include the units. units = [2]
  24. June 2019, Paper 1, Q19(b)(ii) (5 marks): Determine the value of Kp for Equilibrium 1 at 1000 K. Show all your working. Give your answer to 3 significant figures. Kp = [5]
  25. June 2019, Paper 1, Q19(b)(iii) (2 marks): The chemist repeats the experiment in (b) at a different temperature. The chemist finds that the value of Kp is greater than the answer to (b)(ii). Explain whet
  26. June 2019, Paper 1, Q19(b)(iv) (1 mark): Explain the significance of the expression: Kp & 1. [1]
  27. June 2019, Paper 3, Q1(c) (1 mark): What is the partial pressure of O2 (in Pa) in a gas mixture containing 21% O2 by volume and with a total pressure of 1.0 × 105 Pa? partial pressure of O2 = Pa [
  28. June 2018, Paper 1, Q9 (1 mark): The reversible reaction of sulfur dioxide and oxygen to form sulfur trioxide is shown below. 2SO2(g) + O2(g) 2SO3(g) An equilibrium mixture contains 2.4 mol SO2
  29. June 2018, Paper 1, Q18(a) (2 marks): Write an expression for Kc for this equilibrium and state the units. Kc = Units = [2]
  30. June 2018, Paper 1, Q18(b) (4 marks): A chemist mixes together nitrogen and oxygen and pressurises the gases so that their total gas volume is 4.0 dm3. • The mixture is allowed to reach equilibrium
  31. June 2018, Paper 1, Q18(c)(i) (1 mark): Predict, with a reason, whether the forward reaction is exothermic or endothermic. [1]
  32. June 2018, Paper 1, Q18(c)(ii) (3 marks): The chemist increases the pressure of the equilibrium mixture at the same temperature. State, and explain in terms of Kp, how you would expect the equilibrium p
  33. June 2018, Paper 3, Q5(b)(i) (1 mark): Which technique could be used to determine the equilibrium amount of succinic acid? [1]
  34. June 2018, Paper 3, Q5(b)(iv) (1 mark): Kc is the equilibrium constant in terms of equilibrium concentrations. Why can expression 5.1 be used to calculate Kc for this equilibrium? [1]
  35. June 2018, Paper 3, Q5(b)(v) (3 marks): Calculate the value of Kc for this reaction. Show your working. Kc = [3]
  36. June 2017, Paper 1, Q13 (1 mark): A mixture of N2 and O2 gases has a total pressure of 1.42 atm. The mole fraction of N2 is 0.700. What is the partial pressure, in atm, of O2 in the mixture? A 0
  37. June 2017, Paper 1, Q18(b)(i) (1 mark): Why is equilibrium 18.1 a heterogeneous equilibrium? [1]
  38. June 2017, Paper 1, Q18(b)(ii) (1 mark): Write the expression for Kp for equilibrium 18.1. [1]
  39. June 2017, Paper 1, Q20(b)(i) (2 marks): Write the expression for Kc and the units of Kc for this equilibrium. [2]
  40. June 2017, Paper 1, Q20(b)(ii) (4 marks): Determine the amount, in mol, of SO3 in the equilibrium mixture at this temperature. Give your final answer to an appropriate number of significant figures. Sho
  41. June 2017, Paper 3, Q3(c)(ii) (3 marks): Peroxyethanoic acid can be prepared by reacting hydrogen peroxide with ethanoic acid. This is a heterogeneous equilibrium. CH3COOOH(aq) + H2O(l) Kc = 0.37 dm3 m

Questions, mark schemes and examiner’s reports are © OCR, from their published past papers. Plumi isn’t affiliated with any exam board. Want whole papers? Every OCR A-Level Chemistry A paper, or our free OCR-style practice pack.

Rather write your answers by hand on iPad? Plumi marks them against the same mark schemes.