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Compounds, formulae and equations: OCR A‑Level Chemistry A questions

Every OCR A-Level Chemistry A exam question on 2.1.2 Compounds, formulae and equations, 2016–2025, with its mark scheme and examiner’s report.

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1,820 questions

  1. Q4(b)(i)

    June 2024 · Paper 3

    1 mark2.1.2 Compounds, formulae and equations
    The whole paper ↗
    June 2024 Paper 3, question 4(b)(i): Phosphine reacts with oxygen gas to form phosphorus(V) oxide and water. Write the equation for this reaction. [1]

  2. Q4(c)(i)

    June 2024 · Paper 3

    1 mark2.1.2 Compounds, formulae and equations
    The whole paper ↗
    June 2024 Paper 3, question 4(c)(i): Write an equation for the reaction of PCl 5 and ammonium chloride to form P3N3Cl 6. [1]

  3. Q21(b)(ii)

    June 2024 · AS Paper 1

    1 mark2.1.2 Compounds, formulae and equations
    The whole paper ↗
    June 2024 AS Paper 1, question 21(b)(ii): Balance the equation for the reduction of Fe2O3 with carbon monoxide. Fe2O3 + CO Fe + CO2 [1]

  4. Q2(a)(iii)

    June 2024 · AS Paper 2

    2 marks2.1.2 Compounds, formulae and equations
    The whole paper ↗
    June 2024 AS Paper 2, question 2(a)(iii): Mg forms 2+ ions but Cl usually forms 1– ions in their reactions. Explain why. [2]

  5. Q20(d)(i)

    June 2023 · Paper 1

    1 mark2.1.2 Compounds, formulae and equations
    The whole paper ↗
    June 2023 Paper 1, question 20(d)(i): Construct an ionic equation for the reaction of magnesium with an acid. [1]

  6. Q4(a)

    June 2023 · Paper 3

    1 mark2.1.2 Compounds, formulae and equations
    The whole paper ↗
    June 2023 Paper 3, question 4(a): Predict the formula of a Tutton’s salt containing different ions from (NH4)2Cu(SO4)2 • 6H2O. [1]

  7. Q2(b)(i)

    June 2023 · AS Paper 2

    2 marks2.1.2 Compounds, formulae and equations
    The whole paper ↗
    June 2023 AS Paper 2, question 2(b)(i): Write an equation for the formation of barium sulfate in step 2. Include state symbols. [2]

  8. Q21(b)(ii)

    June 2022 · Paper 1

    1 mark2.1.2 Compounds, formulae and equations
    The whole paper ↗
    June 2022 Paper 1, question 21(b)(ii): 10 cm3 of dilute sulfuric acid is added to 10 cm3 of the colourless solution of Ba(OH)2. Write an ionic equation, including state symbols, for the reaction. [1]

  9. Q23(c)

    November 2021 · AS Paper 1

    1 mark2.1.2 Compounds, formulae and equations
    The whole paper ↗
    November 2021 AS Paper 1, question 23(c): A mixture of potassium perchlorate, KCl O4, and aluminium is used in fireworks. When the firework ignites, KCl O4 reacts with aluminium to form potassium chlori

  10. Q17(b)

    November 2020 · Paper 2

    3 marks2.1.2 Compounds, formulae and equations
    The whole paper ↗
    November 2020 Paper 2, question 17(b): Compound C can be prepared by ‘trimerisation’ of propanone using concentrated sulfuric acid as a catalyst. Suggest an equation for this reaction, using molecula

  11. Q2

    November 2020 · AS Paper 1

    1 mark2.1.2 Compounds, formulae and equations
    The whole paper ↗
    November 2020 AS Paper 1, question 2: What is the formula of silver carbonate? A AgCO3 B Ag(CO3)2 C Ag2CO3 D Ag3CO3 Your answer [1]

  12. Q8

    November 2020 · AS Paper 1

    1 mark2.1.2 Compounds, formulae and equations
    The whole paper ↗
    November 2020 AS Paper 1, question 8: The unbalanced equation for the reaction of copper with concentrated nitric acid is shown below. Cu + HNO3 → Cu(NO3)2 + NO2 + H2O What is the number of moles of

  13. Q22(a)(ii)

    November 2020 · AS Paper 1

    1 mark2.1.2 Compounds, formulae and equations
    The whole paper ↗
    November 2020 AS Paper 1, question 22(a)(ii): Write the equation for the reaction of phosphorus with bromine. [1]

  14. Q3(c)(i)

    November 2020 · AS Paper 2

    1 mark2.1.2 Compounds, formulae and equations
    The whole paper ↗
    November 2020 AS Paper 2, question 3(c)(i): H2Se can be prepared by reacting aluminium selenide, Al 2Se3, with water. Aluminium hydroxide and hydrogen selenide are formed. Write the equation for this reac

  15. Q3(a)(i)

    June 2019 · Paper 3

    1 mark2.1.2 Compounds, formulae and equations
    The whole paper ↗
    June 2019 Paper 3, question 3(a)(i): Write the equation for the reduction of Pb2O3 with CH4. [1]

  16. Q8

    June 2019 · AS Paper 1

    1 mark2.1.2 Compounds, formulae and equations
    The whole paper ↗
    June 2019 AS Paper 1, question 8: 3−. 8 A phosphate(V) ion has the formula PO4 What is the formula for copper(I) phosphate(V)? A Cu(PO4)5 B Cu5PO4 C Cu(PO4)3 D Cu3PO4 Your answer [1]

  17. Q21(d)(ii)

    June 2019 · AS Paper 1

    2 marks2.1.2 Compounds, formulae and equations
    The whole paper ↗
    June 2019 AS Paper 1, question 21(d)(ii): Calcium nitride reacts with water to form a solution containing two alkaline compounds. Write an equation for this reaction. [2]

  18. Q6

    June 2018 · Paper 1

    1 mark2.1.2 Compounds, formulae and equations
    The whole paper ↗
    June 2018 Paper 1, question 6: In the Periodic Table, element X is in Group 2 and element Y is in Group 15 (5). What is the likely formula of an ionic compound of X and Y? A X2Y5 B X2Y3 C X3Y

  19. Q1

    June 2018 · AS Paper 1

    1 mark2.1.2 Compounds, formulae and equations
    The whole paper ↗
    June 2018 AS Paper 1, question 1: The electron configuration of element X is: 1s22s22p63s23p4 1 What is the formula of a compound formed when sodium reacts with element X? A NaX B NaX2 C Na2X D

  20. Q15

    June 2018 · AS Paper 1

    1 mark2.1.2 Compounds, formulae and equations
    The whole paper ↗
    June 2018 AS Paper 1, question 15: 1 mol of a compound reacts with 8 mol O2 for complete combustion. What is the formula of the compound? A C4H8 B C4H9OH C C5H11OH D C5H12 Your answer [1]
All 26 questions on Compounds, formulae and equations, as a list
  1. June 2024, Paper 3, Q4(b)(i) (1 mark): Phosphine reacts with oxygen gas to form phosphorus(V) oxide and water. Write the equation for this reaction. [1]
  2. June 2024, Paper 3, Q4(c)(i) (1 mark): Write an equation for the reaction of PCl 5 and ammonium chloride to form P3N3Cl 6. [1]
  3. June 2024, AS Paper 1, Q21(b)(ii) (1 mark): Balance the equation for the reduction of Fe2O3 with carbon monoxide. Fe2O3 + CO Fe + CO2 [1]
  4. June 2024, AS Paper 2, Q2(a)(iii) (2 marks): Mg forms 2+ ions but Cl usually forms 1– ions in their reactions. Explain why. [2]
  5. June 2023, Paper 1, Q20(d)(i) (1 mark): Construct an ionic equation for the reaction of magnesium with an acid. [1]
  6. June 2023, Paper 3, Q4(a) (1 mark): Predict the formula of a Tutton’s salt containing different ions from (NH4)2Cu(SO4)2 • 6H2O. [1]
  7. June 2023, AS Paper 2, Q2(b)(i) (2 marks): Write an equation for the formation of barium sulfate in step 2. Include state symbols. [2]
  8. June 2022, Paper 1, Q21(b)(ii) (1 mark): 10 cm3 of dilute sulfuric acid is added to 10 cm3 of the colourless solution of Ba(OH)2. Write an ionic equation, including state symbols, for the reaction. [1]
  9. November 2021, AS Paper 1, Q23(c) (1 mark): A mixture of potassium perchlorate, KCl O4, and aluminium is used in fireworks. When the firework ignites, KCl O4 reacts with aluminium to form potassium chlori
  10. November 2020, Paper 2, Q17(b) (3 marks): Compound C can be prepared by ‘trimerisation’ of propanone using concentrated sulfuric acid as a catalyst. Suggest an equation for this reaction, using molecula
  11. November 2020, AS Paper 1, Q2 (1 mark): What is the formula of silver carbonate? A AgCO3 B Ag(CO3)2 C Ag2CO3 D Ag3CO3 Your answer [1]
  12. November 2020, AS Paper 1, Q8 (1 mark): The unbalanced equation for the reaction of copper with concentrated nitric acid is shown below. Cu + HNO3 → Cu(NO3)2 + NO2 + H2O What is the number of moles of
  13. November 2020, AS Paper 1, Q22(a)(ii) (1 mark): Write the equation for the reaction of phosphorus with bromine. [1]
  14. November 2020, AS Paper 2, Q3(c)(i) (1 mark): H2Se can be prepared by reacting aluminium selenide, Al 2Se3, with water. Aluminium hydroxide and hydrogen selenide are formed. Write the equation for this reac
  15. June 2019, Paper 3, Q3(a)(i) (1 mark): Write the equation for the reduction of Pb2O3 with CH4. [1]
  16. June 2019, AS Paper 1, Q8 (1 mark): 3−. 8 A phosphate(V) ion has the formula PO4 What is the formula for copper(I) phosphate(V)? A Cu(PO4)5 B Cu5PO4 C Cu(PO4)3 D Cu3PO4 Your answer [1]
  17. June 2019, AS Paper 1, Q21(d)(ii) (2 marks): Calcium nitride reacts with water to form a solution containing two alkaline compounds. Write an equation for this reaction. [2]
  18. June 2018, Paper 1, Q6 (1 mark): In the Periodic Table, element X is in Group 2 and element Y is in Group 15 (5). What is the likely formula of an ionic compound of X and Y? A X2Y5 B X2Y3 C X3Y
  19. June 2018, AS Paper 1, Q1 (1 mark): The electron configuration of element X is: 1s22s22p63s23p4 1 What is the formula of a compound formed when sodium reacts with element X? A NaX B NaX2 C Na2X D
  20. June 2018, AS Paper 1, Q15 (1 mark): 1 mol of a compound reacts with 8 mol O2 for complete combustion. What is the formula of the compound? A C4H8 B C4H9OH C C5H11OH D C5H12 Your answer [1]
  21. June 2018, AS Paper 1, Q22(b)(ii) (1 mark): When exposed to air, phosphine spontaneously ignites, forming P4O10 and water. Construct an equation for this reaction. [1]
  22. June 2018, AS Paper 2, Q2(c)(ii) (2 marks): Sodium selenide reacts with hydrochloric acid to form a toxic gas, B, with a relative molecular mass of 81.0. Identify gas B and write an equation for this reac
  23. June 2017, AS Paper 1, Q24(b)(i) (1 mark): The unbalanced equation for the reaction is shown below. Balance the equation. ……. Al (s) + ……. CH3COOH(aq) → ……. (CH3COO)3Al (aq) + …… H2(g) [1]
  24. June 2016, AS Paper 1, Q2 (1 mark): What is the formula of ammonium sulfide? A NH4S B NH4SO4 C (NH4)2S D (NH4)2SO4 Your answer [1]
  25. June 2016, AS Paper 1, Q24(b) (1 mark): Write an ionic equation for the reaction that the student carries out. Include state symbols. [1]
  26. June 2016, AS Paper 2, Q2(c) (1 mark): Aluminium forms a sulfide, Al2S3. Al2S3 reacts with water to form aluminium hydroxide and hydrogen sulfide, H2S. Write an equation for the reaction of Al2S3 wit

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