Skip to content
Try on iPad

Equilibrium I: Edexcel A‑Level Chemistry questions

Every Edexcel A-Level Chemistry exam question on 10 Equilibrium I, 2016–2025, with its mark scheme and examiner’s report.

Find questions2,028
Calculations

2,028 questions

  1. Q4(b)(i)

    June 2025 · Paper 1

    2 marks10 Equilibrium I
    The whole paper ↗
    June 2025 Paper 1, question 4(b)(i): It is proposed to increase the pressure in the reactor to 70.0 atm. Explain the effect this change would have on the yield of ethanol by referring to the equili

  2. Q5(b)(i)

    June 2025 · Paper 3

    2 marks10 Equilibrium I
    The whole paper ↗
    June 2025 Paper 3, question 5(b)(i): State what is meant by the term ‘dynamic equilibrium’. (2)

  3. Q7(a)(i)

    June 2025 · AS Paper 2

    3 marks10 Equilibrium I9 Kinetics I
    The whole paper ↗
    June 2025 AS Paper 2, question 7(a)(i): Explain why the reaction is carried out at a temperature of 700 K rather than 400 K or 1000 K. (3)

  4. Q7(a)(ii)

    June 2025 · AS Paper 2

    3 marks10 Equilibrium I9 Kinetics I
    The whole paper ↗
    June 2025 AS Paper 2, question 7(a)(ii): Explain why the reaction is carried out at a pressure of 90 atm rather than 40 atm or 140 atm. (3)

  5. Q8(a)(i)

    June 2025 · AS Paper 2

    1 mark10 Equilibrium I
    The whole paper ↗
    June 2025 AS Paper 2, question 8(a)(i): Which is the expression for the equilibrium constant Kc? (1) A Kc = 3[H ][CO] 2 [H O][CH ] 2 4 Kc = [H O][CH ] 2 4 B 3[H ][CO] 2 Kc = [H ] [CO] 3 2 C [H O][CH ]

  6. Q2(a)(i)

    June 2024 · AS Paper 2

    3 marks10 Equilibrium I
    The whole paper ↗
    June 2024 AS Paper 2, question 2(a)(i): Explain the effect on the appearance of the solution of adding a small volume of sodium hydroxide solution to the equilibrium mixture. (3)

  7. Q2(a)(ii)

    June 2024 · AS Paper 2

    1 mark10 Equilibrium I
    The whole paper ↗
    June 2024 AS Paper 2, question 2(a)(ii): Which is the expression for the equilibrium constant, Kc , for this reaction? (1) 2 − 2 + 2 A Kc = [ CrO ] [ H ] 4 2 − [ Cr O ][ H O ] 2 7 2 2 − + B Kc = 2 [ Cr

  8. Q2(b)(i)

    June 2024 · AS Paper 2

    3 marks10 Equilibrium I
    The whole paper ↗
    June 2024 AS Paper 2, question 2(b)(i): Justify all the colour changes of the contents of the syringe during this process. (3)

  9. Q2(b)(ii)

    June 2024 · AS Paper 2

    2 marks10 Equilibrium I
    The whole paper ↗
    June 2024 AS Paper 2, question 2(b)(ii): The syringe is placed into hot water. The contents of the syringe become a darker brown. Explain what can be deduced about the reaction from this change. (2)

  10. Q7

    June 2024 · AS Paper 2

    6 marks10 Equilibrium I9 Kinetics I
    The whole paper ↗
    June 2024 AS Paper 2, question 7: *7 Methanol can be produced by reacting carbon dioxide and hydrogen in the exothermic reaction shown. CO2(g) + 3H2(g)  CH3OH(g) + H2O(g) Discuss, with reasons,

  11. Q5(b)

    June 2023 · Paper 1

    1 mark10 Equilibrium I
    The whole paper ↗
    June 2023 Paper 1, question 5(b): What happens to the position of the equilibrium and the colour of the mixture when the pressure is increased? The volume of the system remains constant. N2O4(g)

  12. Q6

    June 2023 · AS Paper 2

    1 mark10 Equilibrium I
    The whole paper ↗
    June 2023 AS Paper 2, question 6: Ammonium carbamate has the formula NH2COONH4 . When a sample of ammonium carbamate is placed in a sealed tube and heated, it partially decomposes to the compoun

  13. Q7(a)(i)

    June 2022 · AS Paper 2

    2 marks10 Equilibrium I
    The whole paper ↗
    June 2022 AS Paper 2, question 7(a)(i): Calculate the number of moles of NO and Cl2 at equilibrium. (2) Moles of NO Moles of Cl2

  14. Q7(a)(ii)

    June 2022 · AS Paper 2

    3 marks10 Equilibrium I
    The whole paper ↗
    June 2022 AS Paper 2, question 7(a)(ii): Sketch three lines showing the change in concentration over time of the three components of the reaction using the axes given. You should assume that the reacti

  15. Q7(a)(iii)

    June 2022 · AS Paper 2

    1 mark10 Equilibrium I
    The whole paper ↗
    June 2022 AS Paper 2, question 7(a)(iii): The expression for the equilibrium constant, Kc , for this reaction is (1) [ ] l A Kc = 2 NOC [ ][ ] 2 NO C 2 l [ ] 2 NOC l B Kc = [ ] [ ] 2 NO C 2 l [ ][ ] l C

  16. Q7(a)(iv)

    June 2022 · AS Paper 2

    1 mark10 Equilibrium I
    The whole paper ↗
    June 2022 AS Paper 2, question 7(a)(iv): Give the reason why the equilibrium yield of NOCl decreases when the temperature changes from 25 °C to 225 °C. The enthalpy change for the reaction at 25 °C is

  17. Q9(a)

    November 2021 · Paper 3

    2 marks10 Equilibrium I
    The whole paper ↗
    November 2021 Paper 3, question 9(a): The pressure used in the Haber Process is 200 atm. Explain the effect, if any, of increasing the pressure on the equilibrium yield of ammonia. (2)

  18. Q2(b)

    November 2021 · AS Paper 2

    2 marks10 Equilibrium I
    The whole paper ↗
    November 2021 AS Paper 2, question 2(b): Another source gave a different value for the enthalpy change of this reaction. PCl5(g)  PCl3(g) + Cl2(g) ΔrH = +87.9 kJ mol–1 Explain the effect, if any, of i

  19. Q9(a)(iv)

    November 2021 · AS Paper 2

    1 mark10 Equilibrium I
    The whole paper ↗
    November 2021 AS Paper 2, question 9(a)(iv): What is the equilibrium expression for Kc? (1) A Kc = [N ][3H ] 2 2 [2NH ] 3 B Kc = [2NH ] 3 [N ][3H ] 2 2 C Kc = [NH ] 2 3 3 [N ][H ] 2 2 D Kc = [N ][H ] 3 2 2

  20. Q9(b)

    November 2021 · AS Paper 2

    3 marks10 Equilibrium I
    The whole paper ↗
    November 2021 AS Paper 2, question 9(b): In the chemical industry, many processes involve reversible reactions. The product is often removed before equilibrium is attained. Give three reasons why the p
All 42 questions on Equilibrium I, as a list
  1. June 2025, Paper 1, Q4(b)(i) (2 marks): It is proposed to increase the pressure in the reactor to 70.0 atm. Explain the effect this change would have on the yield of ethanol by referring to the equili
  2. June 2025, Paper 3, Q5(b)(i) (2 marks): State what is meant by the term ‘dynamic equilibrium’. (2)
  3. June 2025, AS Paper 2, Q7(a)(i) (3 marks): Explain why the reaction is carried out at a temperature of 700 K rather than 400 K or 1000 K. (3)
  4. June 2025, AS Paper 2, Q7(a)(ii) (3 marks): Explain why the reaction is carried out at a pressure of 90 atm rather than 40 atm or 140 atm. (3)
  5. June 2025, AS Paper 2, Q8(a)(i) (1 mark): Which is the expression for the equilibrium constant Kc? (1) A Kc = 3[H ][CO] 2 [H O][CH ] 2 4 Kc = [H O][CH ] 2 4 B 3[H ][CO] 2 Kc = [H ] [CO] 3 2 C [H O][CH ]
  6. June 2024, AS Paper 2, Q2(a)(i) (3 marks): Explain the effect on the appearance of the solution of adding a small volume of sodium hydroxide solution to the equilibrium mixture. (3)
  7. June 2024, AS Paper 2, Q2(a)(ii) (1 mark): Which is the expression for the equilibrium constant, Kc , for this reaction? (1) 2 − 2 + 2 A Kc = [ CrO ] [ H ] 4 2 − [ Cr O ][ H O ] 2 7 2 2 − + B Kc = 2 [ Cr
  8. June 2024, AS Paper 2, Q2(b)(i) (3 marks): Justify all the colour changes of the contents of the syringe during this process. (3)
  9. June 2024, AS Paper 2, Q2(b)(ii) (2 marks): The syringe is placed into hot water. The contents of the syringe become a darker brown. Explain what can be deduced about the reaction from this change. (2)
  10. June 2024, AS Paper 2, Q7 (6 marks): *7 Methanol can be produced by reacting carbon dioxide and hydrogen in the exothermic reaction shown. CO2(g) + 3H2(g)  CH3OH(g) + H2O(g) Discuss, with reasons,
  11. June 2023, Paper 1, Q5(b) (1 mark): What happens to the position of the equilibrium and the colour of the mixture when the pressure is increased? The volume of the system remains constant. N2O4(g)
  12. June 2023, AS Paper 2, Q6 (1 mark): Ammonium carbamate has the formula NH2COONH4 . When a sample of ammonium carbamate is placed in a sealed tube and heated, it partially decomposes to the compoun
  13. June 2022, AS Paper 2, Q7(a)(i) (2 marks): Calculate the number of moles of NO and Cl2 at equilibrium. (2) Moles of NO Moles of Cl2
  14. June 2022, AS Paper 2, Q7(a)(ii) (3 marks): Sketch three lines showing the change in concentration over time of the three components of the reaction using the axes given. You should assume that the reacti
  15. June 2022, AS Paper 2, Q7(a)(iii) (1 mark): The expression for the equilibrium constant, Kc , for this reaction is (1) [ ] l A Kc = 2 NOC [ ][ ] 2 NO C 2 l [ ] 2 NOC l B Kc = [ ] [ ] 2 NO C 2 l [ ][ ] l C
  16. June 2022, AS Paper 2, Q7(a)(iv) (1 mark): Give the reason why the equilibrium yield of NOCl decreases when the temperature changes from 25 °C to 225 °C. The enthalpy change for the reaction at 25 °C is
  17. November 2021, Paper 3, Q9(a) (2 marks): The pressure used in the Haber Process is 200 atm. Explain the effect, if any, of increasing the pressure on the equilibrium yield of ammonia. (2)
  18. November 2021, AS Paper 2, Q2(b) (2 marks): Another source gave a different value for the enthalpy change of this reaction. PCl5(g)  PCl3(g) + Cl2(g) ΔrH = +87.9 kJ mol–1 Explain the effect, if any, of i
  19. November 2021, AS Paper 2, Q9(a)(iv) (1 mark): What is the equilibrium expression for Kc? (1) A Kc = [N ][3H ] 2 2 [2NH ] 3 B Kc = [2NH ] 3 [N ][3H ] 2 2 C Kc = [NH ] 2 3 3 [N ][H ] 2 2 D Kc = [N ][H ] 3 2 2
  20. November 2021, AS Paper 2, Q9(b) (3 marks): In the chemical industry, many processes involve reversible reactions. The product is often removed before equilibrium is attained. Give three reasons why the p
  21. October 2020, Paper 1, Q7(a)(i) (1 mark): Write the expression for the equilibrium constant, Kc . (1)
  22. October 2020, AS Paper 2, Q4(b)(i) (4 marks): Explain the effects of increasing the pressure on the yield of the products and on the rate of the reaction in Step 1. (4)
  23. October 2020, AS Paper 2, Q4(b)(ii) (3 marks): Step 2 is carried out at a compromise temperature of 500 K. Explain why 500 K is considered to be a compromise for Step 2 by considering what would happen at hi
  24. June 2019, Paper 1, Q10(b) (2 marks): An equilibrium exists in aqueous solution between the chromate(VI) ions and the dichromate(VI) ions. ` Cr2O7 2–(aq) + 2H+(aq) _ 2–(aq) + H2O(l) 2CrO4 Explain an
  25. June 2019, Paper 1, Q10(c) (1 mark): The equilibrium for the reaction between hydrogen gas and an oxide of iron is ` 3Fe(s) + 4H2O(g) Fe3O4(s) + 4H2(g) _ The Kc expression for this equilibrium is (
  26. June 2019, AS Paper 2, Q4(a) (2 marks): Give two characteristics of all reactions at equilibrium. (2)
  27. June 2019, AS Paper 2, Q4(b)(i) (1 mark): How does the equilibrium yield of methanol change if the temperature is increased at constant pressure or the pressure increased at constant temperature? (1) Eq
  28. June 2019, AS Paper 2, Q4(b)(ii) (2 marks): Explain your answer to (b)(i). (2)
  29. June 2018, Paper 1, Q6(b)(i) (1 mark): Give a reason why the magnesium hydroxide is not included in the expression for Kc . (1)
  30. June 2018, Paper 1, Q6(b)(iv) (1 mark): Which graph shows the change in the concentration of the Mg2+(aq) ions when some solid magnesium hydroxide is shaken with water and left to reach equilibrium? (
  31. June 2018, Paper 1, Q6(b)(v) (4 marks): Predict the effect, if any, of adding each of the following to a saturated solution of magnesium hydroxide in contact with solid magnesium hydroxide. Justify yo
  32. June 2018, AS Paper 2, Q3(a) (2 marks): Write the expression, including units, for the equilibrium constant Kc for this reaction. (2) Expression Units
  33. June 2018, AS Paper 2, Q3(c)(i) (2 marks): Explain the effect, if any, of increasing pressure on the equilibrium yield of NO in this reaction. 4NH3(g) + 5O2(g)  4NO(g) + 6H2O(g) (2)
  34. June 2018, AS Paper 2, Q5(c)(i) (2 marks): In stage 1, chlorine is reacted with ethene at a temperature between 50 °C and 80 °C CH2Cl ΔH = −178 kJ mol−1 Cl2 + CH2 CH2  CH2Cl Give one reason why a temper
  35. June 2017, Paper 1, Q10(a)(ii) (2 marks): Explain the effect of an increase in pressure on the equilibrium position of this reaction. (2)
  36. June 2017, Paper 3, Q9(a)(i) (1 mark): Write the expression for the equilibrium constant, Kc, for this reaction. (1)
  37. June 2017, AS Paper 2, Q6(a) (6 marks): Evaluate the feasibility of each of these changes in terms of their effect on the rate, yield and economics of the reaction. (6)
  38. June 2017, AS Paper 2, Q6(c)(i) (1 mark): Write the expression for the equilibrium constant Kc for this reaction. 2SO2(g) + O2(g) ` _ 2SO3(g) (1)
  39. June 2017, AS Paper 2, Q6(c)(ii) (1 mark): What are the units, if any, of the equilibrium constant, Kc? (1) A mol dm–3 B dm3 mol–1 C no units D mol2 dm–6
  40. June 2016, AS Paper 2, Q2(c)(i) (1 mark): State the effect, if any, on the yield of ethanol when the temperature is increased. (1)
  41. June 2016, AS Paper 2, Q2(c)(ii) (1 mark): State the effect, if any, on the yield of ethanol when the pressure is decreased. (1)
  42. June 2016, AS Paper 2, Q2(c)(iii) (1 mark): What is the expression for the equilibrium constant, Kc, for this reaction? (1) [ ] [ ] C H (g) + H O(g) 2 4 2 A [ ] C H OH(g) 2 5 [ ][ ] C H (g) H O(g) 2 4 2 B

Questions, mark schemes and examiner’s reports are © Pearson Edexcel, from their published past papers. Plumi isn’t affiliated with any exam board. Want whole papers? Every Edexcel A-Level Chemistry paper.

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