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The halogens: OCR A‑Level Chemistry A questions

Every OCR A-Level Chemistry A exam question on 3.1.3 The halogens, 2016–2025, with its mark scheme and examiner’s report.

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1,820 questions

  1. Q16(c)

    June 2025 · Paper 1

    3 marks3.1.3 The halogens
    The whole paper ↗
    June 2025 Paper 1, question 16(c): A student adds an aqueous solution of bromine, Br2(aq), to two test tubes. The student adds aqueous sodium iodide, NaI(aq), to the Br2(aq) in one test tube, and

  2. Q22(a)

    June 2025 · AS Paper 1

    3 marks3.1.3 The halogens
    The whole paper ↗
    June 2025 AS Paper 1, question 22(a): An aqueous solution of bromine reacts with cold aqueous sodium hydroxide in a disproportionation reaction. The equation is shown below. Br2(aq) + 2NaOH(aq) NaBr

  3. Q22(b)(i)

    June 2025 · AS Paper 1

    3 marks3.1.3 The halogens
    The whole paper ↗
    June 2025 AS Paper 1, question 22(b)(i): Explain why chlorine reacts more vigorously than bromine. [3]

  4. Q22(b)(ii)

    June 2025 · AS Paper 1

    1 mark3.1.3 The halogens
    The whole paper ↗
    June 2025 AS Paper 1, question 22(b)(ii): Chlorine is used in water treatment. State one disadvantage of treating water with chlorine. [1]

  5. Q5

    June 2024 · Paper 1

    1 mark3.1.3 The halogens
    The whole paper ↗
    June 2024 Paper 1, question 5: Which statement explains the trend in boiling points down the halogens group? A The bond enthalpy of the covalent bonds increases. B The halogens become less el

  6. Q6

    June 2024 · Paper 1

    1 mark3.1.3 The halogens
    The whole paper ↗
    June 2024 Paper 1, question 6: Which equation does not represent a disproportionation reaction? A Cl 2 + H2O HCl O + HCl B Cl 2 + 2NaOH NaCl O + NaCl + H2O C 4KCl O3 KCl + 3KCl O4 D 4HCl + Mn

  7. Q14

    June 2024 · Paper 1

    1 mark3.1.3 The halogens
    The whole paper ↗
    June 2024 Paper 1, question 14: Chlorine has the electron configuration [Ne]3s23p5. Which statement(s) about chlorine is/are correct when it reacts in redox reactions? 1 It can gain one electr

  8. Q20(a)(i)

    June 2024 · Paper 1

    1 mark3.1.3 The halogens
    The whole paper ↗
    June 2024 Paper 1, question 20(a)(i): Chlorine is used to treat water in large-scale water treatment plants. Suggest why chlorine is added to water in large-scale water treatment plants. [1]

  9. Q20(a)(ii)

    June 2024 · Paper 1

    2 marks3.1.3 The halogens
    The whole paper ↗
    June 2024 Paper 1, question 20(a)(ii): Sea water contains aqueous bromide ions. Chlorine is used to extract bromine from sea water. Construct the ionic equation for this reaction and explain why chlo

  10. Q2(b)(i)

    June 2024 · Paper 3

    1 mark3.1.3 The halogens
    The whole paper ↗
    June 2024 Paper 3, question 2(b)(i): Write an ionic equation, with state symbols, for the reaction in Step 2. [1]

  11. Q8

    June 2024 · AS Paper 1

    1 mark3.1.3 The halogens
    The whole paper ↗
    June 2024 AS Paper 1, question 8: In the UK, water companies typically treat drinking water with chlorine gas at a concentration of 0.500 mg dm–3 or less. Which statement about UK drinking water

  12. Q9

    June 2024 · AS Paper 1

    1 mark3.1.3 The halogens
    The whole paper ↗
    June 2024 AS Paper 1, question 9: Which reaction does not show disproportionation of chlorine? A MnO2 + 4HCl MnCl 2 + Cl 2 + 2H2O B Cl 2 + H2O HCl + HCl O C 2Cl O2 + 2NaOH NaCl O2 + NaCl O3 + H2

  13. Q1(g)

    June 2023 · Paper 3

    1 mark3.1.3 The halogens
    The whole paper ↗
    June 2023 Paper 3, question 1(g): The element that forms 1– ions most readily. [1]

  14. Q1

    June 2023 · AS Paper 1

    1 mark3.1.3 The halogens
    The whole paper ↗
    June 2023 AS Paper 1, question 1: Which statement explains the trend in boiling points down the halogens group? A Covalent bonds become stronger. B Induced dipole–dipole interactions (London for

  15. Q3(a)

    June 2023 · AS Paper 2

    6 marks3.1.3 The halogens2.1.3 Amount of substance
    The whole paper ↗
    June 2023 AS Paper 2, question 3(a): This question is about halogens and halogen compounds. (a)* Seawater contains very small quantities of dissolved iodide ions. The concentration of potassium iod

  16. Q3(b)

    June 2023 · AS Paper 2

    3 marks3.1.3 The halogens
    The whole paper ↗
    June 2023 AS Paper 2, question 3(b): Chlorine reacts with calcium hydroxide to form Ca(OCl )2, which is the active ingredient in bleaching powder. 2Cl 2 + 2Ca(OH)2 CaCl 2 + Ca(OCl )2 + 2H2O This is

  17. Q4(b)(i)

    June 2022 · Paper 3

    1 mark3.1.3 The halogens
    The whole paper ↗
    June 2022 Paper 3, question 4(b)(i): Explain why the Cl – concentration drops sharply at time = t1. [1]

  18. Q10

    June 2022 · AS Paper 1

    1 mark3.1.3 The halogens
    The whole paper ↗
    June 2022 AS Paper 1, question 10: What is the correct explanation for the trend in the boiling points of chlorine, bromine, and iodine down the group? A Bond enthalpy increases. B Chemical react

  19. Q24(a)(i)

    June 2022 · AS Paper 1

    1 mark3.1.3 The halogens
    The whole paper ↗
    June 2022 AS Paper 1, question 24(a)(i): What is meant by the term disproportionation? [1]

  20. Q24(a)(ii)

    June 2022 · AS Paper 1

    3 marks3.1.3 The halogens
    The whole paper ↗
    June 2022 AS Paper 1, question 24(a)(ii): Construct the equation for the reaction of chlorine with dilute sodium hydroxide. Use your equation to explain that disproportionation has taken place. Equation
All 40 questions on The halogens, as a list
  1. June 2025, Paper 1, Q16(c) (3 marks): A student adds an aqueous solution of bromine, Br2(aq), to two test tubes. The student adds aqueous sodium iodide, NaI(aq), to the Br2(aq) in one test tube, and
  2. June 2025, AS Paper 1, Q22(a) (3 marks): An aqueous solution of bromine reacts with cold aqueous sodium hydroxide in a disproportionation reaction. The equation is shown below. Br2(aq) + 2NaOH(aq) NaBr
  3. June 2025, AS Paper 1, Q22(b)(i) (3 marks): Explain why chlorine reacts more vigorously than bromine. [3]
  4. June 2025, AS Paper 1, Q22(b)(ii) (1 mark): Chlorine is used in water treatment. State one disadvantage of treating water with chlorine. [1]
  5. June 2024, Paper 1, Q5 (1 mark): Which statement explains the trend in boiling points down the halogens group? A The bond enthalpy of the covalent bonds increases. B The halogens become less el
  6. June 2024, Paper 1, Q6 (1 mark): Which equation does not represent a disproportionation reaction? A Cl 2 + H2O HCl O + HCl B Cl 2 + 2NaOH NaCl O + NaCl + H2O C 4KCl O3 KCl + 3KCl O4 D 4HCl + Mn
  7. June 2024, Paper 1, Q14 (1 mark): Chlorine has the electron configuration [Ne]3s23p5. Which statement(s) about chlorine is/are correct when it reacts in redox reactions? 1 It can gain one electr
  8. June 2024, Paper 1, Q20(a)(i) (1 mark): Chlorine is used to treat water in large-scale water treatment plants. Suggest why chlorine is added to water in large-scale water treatment plants. [1]
  9. June 2024, Paper 1, Q20(a)(ii) (2 marks): Sea water contains aqueous bromide ions. Chlorine is used to extract bromine from sea water. Construct the ionic equation for this reaction and explain why chlo
  10. June 2024, Paper 3, Q2(b)(i) (1 mark): Write an ionic equation, with state symbols, for the reaction in Step 2. [1]
  11. June 2024, AS Paper 1, Q8 (1 mark): In the UK, water companies typically treat drinking water with chlorine gas at a concentration of 0.500 mg dm–3 or less. Which statement about UK drinking water
  12. June 2024, AS Paper 1, Q9 (1 mark): Which reaction does not show disproportionation of chlorine? A MnO2 + 4HCl MnCl 2 + Cl 2 + 2H2O B Cl 2 + H2O HCl + HCl O C 2Cl O2 + 2NaOH NaCl O2 + NaCl O3 + H2
  13. June 2023, Paper 3, Q1(g) (1 mark): The element that forms 1– ions most readily. [1]
  14. June 2023, AS Paper 1, Q1 (1 mark): Which statement explains the trend in boiling points down the halogens group? A Covalent bonds become stronger. B Induced dipole–dipole interactions (London for
  15. June 2023, AS Paper 2, Q3(a) (6 marks): This question is about halogens and halogen compounds. (a)* Seawater contains very small quantities of dissolved iodide ions. The concentration of potassium iod
  16. June 2023, AS Paper 2, Q3(b) (3 marks): Chlorine reacts with calcium hydroxide to form Ca(OCl )2, which is the active ingredient in bleaching powder. 2Cl 2 + 2Ca(OH)2 CaCl 2 + Ca(OCl )2 + 2H2O This is
  17. June 2022, Paper 3, Q4(b)(i) (1 mark): Explain why the Cl – concentration drops sharply at time = t1. [1]
  18. June 2022, AS Paper 1, Q10 (1 mark): What is the correct explanation for the trend in the boiling points of chlorine, bromine, and iodine down the group? A Bond enthalpy increases. B Chemical react
  19. June 2022, AS Paper 1, Q24(a)(i) (1 mark): What is meant by the term disproportionation? [1]
  20. June 2022, AS Paper 1, Q24(a)(ii) (3 marks): Construct the equation for the reaction of chlorine with dilute sodium hydroxide. Use your equation to explain that disproportionation has taken place. Equation
  21. November 2021, Paper 1, Q13 (1 mark): Which statement(s) explain(s) the trend in boiling points down the halogens group? 1: The induced dipole–dipole interactions (London forces) become stronger. 2:
  22. November 2021, AS Paper 1, Q23(a) (1 mark): Chlorine is used to kill bacteria in drinking water. State one risk in using chlorine in drinking water. [1]
  23. November 2021, AS Paper 1, Q23(d) (5 marks): A student investigates the trend in reactivity of the halogens Cl 2, Br2 and I2. The student is supplied with: • solutions of Cl 2, Br2 and I2 in cyclohexane (a
  24. November 2020, Paper 1, Q21(a) (5 marks): A student adds a solution of bromine in an organic solvent to two test tubes. The student adds aqueous sodium chloride to one test tube, and aqueous sodium iodi
  25. November 2020, Paper 1, Q21(b) (1 mark): Chlorine is used in water treatment. State one benefit and one risk of using chlorine in water treatment. Benefit Risk [1]
  26. November 2020, AS Paper 2, Q3(d)(ii) (3 marks): This reaction is an example of disproportionation. Use oxidation numbers to explain why. Include the meaning of the term disproportionation. [3]
  27. June 2019, Paper 1, Q2 (1 mark): Which statement about the reactions of halogens with halide ions is correct? I2(aq) can oxidise Br−(aq). A Cl 2(aq) can reduce Br−(aq). B Br−(aq) can reduce Cl
  28. June 2019, AS Paper 1, Q23(a) (3 marks): The boiling points of the halogens are shown in the table. Boiling point Halogen / K fluorine 85 chlorine 239 bromine 332 iodine 457 astatine 503 Explain the tr
  29. June 2018, Paper 1, Q20(a) (3 marks): The halogens show trends in their properties down the group. The boiling points of three halogens are shown below. Halogen Boiling point / °C Chlorine –35 Bromi
  30. June 2018, Paper 3, Q1(a)(v) (1 mark): An element which reacts with water to form an acidic solution. [1]
  31. June 2018, AS Paper 2, Q3(a)(i) (1 mark): Write an ionic equation for the reaction. [1]
  32. June 2018, AS Paper 2, Q3(a)(ii) (3 marks): Explain why iodine is less reactive than bromine. [3]
  33. June 2018, AS Paper 2, Q3(b)(i) (3 marks): Iodine reacts with water as shown below. I2 + H2O HI + HIO Using oxidation numbers, explain why this reaction is a disproportionation. [3]
  34. June 2018, AS Paper 2, Q3(b)(ii) (1 mark): Chlorine is used to purify water on a large scale. State one disadvantage of using chlorine for the purification of drinking water. [1]
  35. June 2017, AS Paper 1, Q9 (1 mark): What is the best explanation for the trend in boiling points down the halogens group? A The covalent bonds become stronger. B The hydrogen bonds become stronger
  36. June 2017, AS Paper 1, Q10 (1 mark): Which silver compound is insoluble in concentrated NH3(aq)? A AgNO3 B AgCl C AgBr D AgI Your answer [1]
  37. June 2016, AS Paper 1, Q23(a)(ii) (2 marks): Write an ionic equation for this reaction and state why this reaction takes place in terms of reactivity of the halogens. [2]
  38. June 2016, AS Paper 1, Q23(b) (1 mark): Chlorine is used in water treatment. State one benefit and one risk of chlorine in water treatment. Benefit Risk [1]
  39. June 2016, AS Paper 1, Q23(c)(i) (1 mark): State the reagent needed for these precipitation reactions. [1]
  40. June 2016, AS Paper 1, Q23(c)(ii) (1 mark): How would the appearance of the precipitates allow you to distinguish between chloride, bromide and iodide ions? Chloride Bromide Iodide [1]

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