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Equilibria (acid–base): OCR A‑Level Chemistry B questions

Every OCR A-Level Chemistry B exam question on EL Equilibria (acid–base) (specification points EL(t)–(u)), 2016–2025, with its mark scheme and examiner’s report.

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2,049 questions

  1. Q1(a)(i)

    June 2025 · Paper 3

    2 marksEL Equilibria (acid–base)
    The whole paper ↗
    June 2025 Paper 3, question 1(a)(i): The term ‘alkaline’ refers to oxides and hydroxides of the Group 2 elements. Explain why calcium oxide is described as alkaline. Include an appropriate equation

  2. Q3(b)

    June 2025 · AS Paper 2

    4 marksEL Equilibria (acid–base)
    The whole paper ↗
    June 2025 AS Paper 2, question 3(b): A student makes a pure sample of hydrated magnesium sulfate using magnesium carbonate. Describe and explain the method the student should use. [4]

  3. Q4

    June 2024 · AS Paper 1

    1 markEL Equilibria (acid–base)
    The whole paper ↗
    June 2024 AS Paper 1, question 4: Magnesium oxide reacts with dilute hydrochloric acid. What is correct for this reaction? A A gas is given off. B A green solution of a salt is formed. C It is a

  4. Q1(a)

    June 2023 · AS Paper 2

    1 markEL Equilibria (acid–base)
    The whole paper ↗
    June 2023 AS Paper 2, question 1(a): Write an equation to show the ions formed when calcium oxide reacts with water. [1]

  5. Q1(b)

    June 2023 · AS Paper 2

    2 marksEL Equilibria (acid–base)
    The whole paper ↗
    June 2023 AS Paper 2, question 1(b): A student shakes a small amount of magnesium oxide in a test tube with water. A white suspension is formed. The student then adds dilute hydrochloric acid, drop

  6. Q1(b)(i)

    June 2022 · Paper 2

    2 marksEL Equilibria (acid–base)
    The whole paper ↗
    June 2022 Paper 2, question 1(b)(i): A hazard warning for Portland cement states that it is alkaline. One of the ingredients in the table reacts with water to form an alkaline solution. Write an eq

  7. Q1(b)(ii)

    June 2022 · Paper 2

    1 markEL Equilibria (acid–base)
    The whole paper ↗
    June 2022 Paper 2, question 1(b)(ii): When Portland cement sets, the calcium oxide absorbs carbon dioxide from the air. Suggest an equation for the reaction that occurs. [1]

  8. Q1(e)

    June 2022 · AS Paper 2

    4 marksEL Equilibria (acid–base)
    The whole paper ↗
    June 2022 AS Paper 2, question 1(e): A student is asked to prepare a sample of hydrated magnesium chloride crystals (containing water of crystallisation) starting from solid magnesium oxide. The st

  9. Q2

    November 2021 · AS Paper 1

    1 markEL Equilibria (acid–base)
    The whole paper ↗
    November 2021 AS Paper 1, question 2: Which statement is correct for the properties of strontium hydroxide? A It does not react with dilute acids. B It is alkaline in solution. C It is more soluble

  10. Q7

    November 2020 · AS Paper 1

    1 markEL Equilibria (acid–base)
    The whole paper ↗
    November 2020 AS Paper 1, question 7: A student wants to make a pure sample of insoluble lead chloride. Which substance should the student react with hydrochloric acid? A Lead B Lead carbonate C Lea

  11. Q22(a)

    June 2019 · AS Paper 1

    1 markEL Equilibria (acid–base)
    The whole paper ↗
    June 2019 AS Paper 1, question 22(a): Suggest why the removal of carbon dioxide was necessary. [1]

  12. Q5(e)

    June 2017 · Paper 2

    3 marksEL Equilibria (acid–base)
    The whole paper ↗
    June 2017 Paper 2, question 5(e): The article describes several methods of neutralising the acidity in paper. One of these is ‘washing in a bath of mild alkali’. Describe two other methods given

  13. Q22(c)(ii)

    June 2017 · AS Paper 1

    2 marksEL Equilibria (acid–base)
    The whole paper ↗
    June 2017 AS Paper 1, question 22(c)(ii): The students’ method would not produce a pure dry sample of lead chloride. State how to improve the method. [2]

  14. Q21(c)(i)

    June 2016 · AS Paper 1

    4 marksEL Equilibria (acid–base)
    The whole paper ↗
    June 2016 AS Paper 1, question 21(c)(i): Describe the steps in their method (without details of the apparatus used). [4]

  15. Q21(c)(ii)

    June 2016 · AS Paper 1

    3 marksEL Equilibria (acid–base)
    The whole paper ↗
    June 2016 AS Paper 1, question 21(c)(ii): The students calculated the mass of crystals they were expecting and found that the percentage yield of their process was much less than 100%. Some students giv

  16. Q2(a)

    June 2016 · AS Paper 2

    1 markEL Equilibria (acid–base)
    The whole paper ↗
    June 2016 AS Paper 2, question 2(a): The student tests a small sample of the medicine with universal indicator. Suggest a pH value that would be obtained by the student. [1]
All 16 questions on Equilibria (acid–base), as a list
  1. June 2025, Paper 3, Q1(a)(i) (2 marks): The term ‘alkaline’ refers to oxides and hydroxides of the Group 2 elements. Explain why calcium oxide is described as alkaline. Include an appropriate equation
  2. June 2025, AS Paper 2, Q3(b) (4 marks): A student makes a pure sample of hydrated magnesium sulfate using magnesium carbonate. Describe and explain the method the student should use. [4]
  3. June 2024, AS Paper 1, Q4 (1 mark): Magnesium oxide reacts with dilute hydrochloric acid. What is correct for this reaction? A A gas is given off. B A green solution of a salt is formed. C It is a
  4. June 2023, AS Paper 2, Q1(a) (1 mark): Write an equation to show the ions formed when calcium oxide reacts with water. [1]
  5. June 2023, AS Paper 2, Q1(b) (2 marks): A student shakes a small amount of magnesium oxide in a test tube with water. A white suspension is formed. The student then adds dilute hydrochloric acid, drop
  6. June 2022, Paper 2, Q1(b)(i) (2 marks): A hazard warning for Portland cement states that it is alkaline. One of the ingredients in the table reacts with water to form an alkaline solution. Write an eq
  7. June 2022, Paper 2, Q1(b)(ii) (1 mark): When Portland cement sets, the calcium oxide absorbs carbon dioxide from the air. Suggest an equation for the reaction that occurs. [1]
  8. June 2022, AS Paper 2, Q1(e) (4 marks): A student is asked to prepare a sample of hydrated magnesium chloride crystals (containing water of crystallisation) starting from solid magnesium oxide. The st
  9. November 2021, AS Paper 1, Q2 (1 mark): Which statement is correct for the properties of strontium hydroxide? A It does not react with dilute acids. B It is alkaline in solution. C It is more soluble
  10. November 2020, AS Paper 1, Q7 (1 mark): A student wants to make a pure sample of insoluble lead chloride. Which substance should the student react with hydrochloric acid? A Lead B Lead carbonate C Lea
  11. June 2019, AS Paper 1, Q22(a) (1 mark): Suggest why the removal of carbon dioxide was necessary. [1]
  12. June 2017, Paper 2, Q5(e) (3 marks): The article describes several methods of neutralising the acidity in paper. One of these is ‘washing in a bath of mild alkali’. Describe two other methods given
  13. June 2017, AS Paper 1, Q22(c)(ii) (2 marks): The students’ method would not produce a pure dry sample of lead chloride. State how to improve the method. [2]
  14. June 2016, AS Paper 1, Q21(c)(i) (4 marks): Describe the steps in their method (without details of the apparatus used). [4]
  15. June 2016, AS Paper 1, Q21(c)(ii) (3 marks): The students calculated the mass of crystals they were expecting and found that the percentage yield of their process was much less than 100%. Some students giv
  16. June 2016, AS Paper 2, Q2(a) (1 mark): The student tests a small sample of the medicine with universal indicator. Suggest a pH value that would be obtained by the student. [1]

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