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Transition elements: OCR A‑Level Chemistry A questions

Every OCR A-Level Chemistry A exam question on 5.3.1 Transition elements, 2016–2025, with its mark scheme and examiner’s report.

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1,820 questions

  1. Q15

    June 2025 · Paper 1

    1 mark5.3.1 Transition elements
    The whole paper ↗
    June 2025 Paper 1, question 15: Chromium forms the complex ions [Cr(NH3)6]3+ and [Cr(OH)6]3–. Which statement(s) about the complexes is / are correct? 1 Chromium is in the same oxidation state

  2. Q21(a)(i)

    June 2025 · Paper 1

    2 marks5.3.1 Transition elements
    The whole paper ↗
    June 2025 Paper 1, question 21(a)(i): Complete the electron configuration of an Fe atom: 1s2 a Cu2+ ion: 1s2 [2]

  3. Q21(a)(ii)

    June 2025 · Paper 1

    2 marks5.3.1 Transition elements
    The whole paper ↗
    June 2025 Paper 1, question 21(a)(ii): Solutions of iron(II) sulfate, FeSO4, and copper(II) sulfate, CuSO4, can be distinguished by adding aqueous sodium hydroxide. Describe what would be observed wh

  4. Q21(b)(i)

    June 2025 · Paper 1

    1 mark5.3.1 Transition elements
    The whole paper ↗
    June 2025 Paper 1, question 21(b)(i): What is meant by a monodentate ligand? [1]

  5. Q21(b)(ii)

    June 2025 · Paper 1

    4 marks2.1.3 Amount of substance5.3.1 Transition elements
    The whole paper ↗
    June 2025 Paper 1, question 21(b)(ii): An iron(II) complex contains two different ligands: C5H5N, and Cl –. The complex has a molar mass of 442.8 g mol–1 and the following percentage composition by m

  6. Q21(c)

    June 2025 · Paper 1

    2 marks5.3.1 Transition elements
    The whole paper ↗
    June 2025 Paper 1, question 21(c): Aqueous copper(II) sulfate reacts with salicylic acid to form a complex ion which has two stereoisomers. One isomer of the complex ion is shown: 2– O O O Cu O O

  7. Q4(b)(ii)

    June 2025 · Paper 3

    3 marks5.3.1 Transition elements
    The whole paper ↗
    June 2025 Paper 3, question 4(b)(ii): Complex A can be prepared by reacting an aqueous solution of nickel(II) sulfate with amino acid B and potassium hydroxide. Aqueous nickel(II) sulfate contains t

  8. Q4(b)(iii)

    June 2025 · Paper 3

    1 mark5.3.1 Transition elements
    The whole paper ↗
    June 2025 Paper 3, question 4(b)(iii): Complete the 3D diagram below to show a stereoisomer of complex A. OH2 Ni OH2 [1]

  9. Q22(a)

    June 2024 · Paper 1

    2 marks2.2.1 Electron structure5.3.1 Transition elements
    The whole paper ↗
    June 2024 Paper 1, question 22(a): Iron is in the d block of the periodic table and contains s, p and d orbitals. • Draw diagrams to show the shapes of an s orbital and a p orbital. Complete the

  10. Q22(b)(i)

    June 2024 · Paper 1

    3 marks5.3.1 Transition elements
    The whole paper ↗
    June 2024 Paper 1, question 22(b)(i): Suggest the formulae of A, B and C. Complex ion A: Solid B: Complex ion C: [3]

  11. Q22(b)(ii)

    June 2024 · Paper 1

    2 marks5.3.1 Transition elements
    The whole paper ↗
    June 2024 Paper 1, question 22(b)(ii): Cobalt (III) forms an octahedral complex ion D, which contains both ammonia and chloride ligands. Complex ion D has a molar mass of 197.9 g mol–1. Determine the

  12. Q22(c)

    June 2024 · Paper 1

    5 marks5.3.1 Transition elements5.1.3 Acids, bases and buffers
    The whole paper ↗
    June 2024 Paper 1, question 22(c): Red blood cells contain haemoglobin which transports oxygen around the body. For efficient transportation of oxygen, healthy human blood must be maintained at a

  13. Q3(a)(i)

    June 2024 · Paper 3

    2 marks5.3.1 Transition elements
    The whole paper ↗
    June 2024 Paper 3, question 3(a)(i): Explain what is meant by the term bidentate ligand. [2]

  14. Q3(a)(ii)

    June 2024 · Paper 3

    3 marks5.3.1 Transition elements
    The whole paper ↗
    June 2024 Paper 3, question 3(a)(ii): A complex ion E contains three C2O4 Complex ion E exists as a mixture of two optical isomers. Draw 3D diagrams to show the structures of the optical isomers of

  15. Q14

    June 2023 · Paper 1

    1 mark5.3.1 Transition elements
    The whole paper ↗
    June 2023 Paper 1, question 14: Which statement(s) is/are correct for the anti-cancer complex Pt(NH3)2Cl 2? 1 It has bond angles of 90º. 2 The oxidation number of Pt is +4. 3 It forms both opt

  16. Q22(a)

    June 2023 · Paper 1

    6 marks5.3.1 Transition elements
    The whole paper ↗
    June 2023 Paper 1, question 22(a): This question is about the d-block elements in Period 4 of the periodic table (Sc to Zn). (a)* Explain, with examples from Period 4, what is meant by the terms

  17. Q22(b)(i)

    June 2023 · Paper 1

    2 marks5.3.1 Transition elements
    The whole paper ↗
    June 2023 Paper 1, question 22(b)(i): Describe precipitation reactions using either copper or chromium ions as examples. Include equations. [2]

  18. Q22(b)(ii)

    June 2023 · Paper 1

    2 marks5.3.1 Transition elements
    The whole paper ↗
    June 2023 Paper 1, question 22(b)(ii): Describe ligand substitution reactions using either copper or chromium ions as examples. Include equations. [2]

  19. Q22(c)

    June 2023 · Paper 1

    2 marks5.3.1 Transition elements
    The whole paper ↗
    June 2023 Paper 1, question 22(c): The ethanedioate ion, C2O4 A complex ion of cobalt(III) contains two ethanedioate ligands and two water ligands. Determine the charge of this complex ion and th

  20. Q1(d)

    June 2023 · Paper 3

    2 marks5.3.1 Transition elements
    The whole paper ↗
    June 2023 Paper 3, question 1(d): The two elements with atoms containing five unpaired electrons. [2]
All 58 questions on Transition elements, as a list
  1. June 2025, Paper 1, Q15 (1 mark): Chromium forms the complex ions [Cr(NH3)6]3+ and [Cr(OH)6]3–. Which statement(s) about the complexes is / are correct? 1 Chromium is in the same oxidation state
  2. June 2025, Paper 1, Q21(a)(i) (2 marks): Complete the electron configuration of an Fe atom: 1s2 a Cu2+ ion: 1s2 [2]
  3. June 2025, Paper 1, Q21(a)(ii) (2 marks): Solutions of iron(II) sulfate, FeSO4, and copper(II) sulfate, CuSO4, can be distinguished by adding aqueous sodium hydroxide. Describe what would be observed wh
  4. June 2025, Paper 1, Q21(b)(i) (1 mark): What is meant by a monodentate ligand? [1]
  5. June 2025, Paper 1, Q21(b)(ii) (4 marks): An iron(II) complex contains two different ligands: C5H5N, and Cl –. The complex has a molar mass of 442.8 g mol–1 and the following percentage composition by m
  6. June 2025, Paper 1, Q21(c) (2 marks): Aqueous copper(II) sulfate reacts with salicylic acid to form a complex ion which has two stereoisomers. One isomer of the complex ion is shown: 2– O O O Cu O O
  7. June 2025, Paper 3, Q4(b)(ii) (3 marks): Complex A can be prepared by reacting an aqueous solution of nickel(II) sulfate with amino acid B and potassium hydroxide. Aqueous nickel(II) sulfate contains t
  8. June 2025, Paper 3, Q4(b)(iii) (1 mark): Complete the 3D diagram below to show a stereoisomer of complex A. OH2 Ni OH2 [1]
  9. June 2024, Paper 1, Q22(a) (2 marks): Iron is in the d block of the periodic table and contains s, p and d orbitals. • Draw diagrams to show the shapes of an s orbital and a p orbital. Complete the
  10. June 2024, Paper 1, Q22(b)(i) (3 marks): Suggest the formulae of A, B and C. Complex ion A: Solid B: Complex ion C: [3]
  11. June 2024, Paper 1, Q22(b)(ii) (2 marks): Cobalt (III) forms an octahedral complex ion D, which contains both ammonia and chloride ligands. Complex ion D has a molar mass of 197.9 g mol–1. Determine the
  12. June 2024, Paper 1, Q22(c) (5 marks): Red blood cells contain haemoglobin which transports oxygen around the body. For efficient transportation of oxygen, healthy human blood must be maintained at a
  13. June 2024, Paper 3, Q3(a)(i) (2 marks): Explain what is meant by the term bidentate ligand. [2]
  14. June 2024, Paper 3, Q3(a)(ii) (3 marks): A complex ion E contains three C2O4 Complex ion E exists as a mixture of two optical isomers. Draw 3D diagrams to show the structures of the optical isomers of
  15. June 2023, Paper 1, Q14 (1 mark): Which statement(s) is/are correct for the anti-cancer complex Pt(NH3)2Cl 2? 1 It has bond angles of 90º. 2 The oxidation number of Pt is +4. 3 It forms both opt
  16. June 2023, Paper 1, Q22(a) (6 marks): This question is about the d-block elements in Period 4 of the periodic table (Sc to Zn). (a)* Explain, with examples from Period 4, what is meant by the terms
  17. June 2023, Paper 1, Q22(b)(i) (2 marks): Describe precipitation reactions using either copper or chromium ions as examples. Include equations. [2]
  18. June 2023, Paper 1, Q22(b)(ii) (2 marks): Describe ligand substitution reactions using either copper or chromium ions as examples. Include equations. [2]
  19. June 2023, Paper 1, Q22(c) (2 marks): The ethanedioate ion, C2O4 A complex ion of cobalt(III) contains two ethanedioate ligands and two water ligands. Determine the charge of this complex ion and th
  20. June 2023, Paper 3, Q1(d) (2 marks): The two elements with atoms containing five unpaired electrons. [2]
  21. June 2023, Paper 3, Q4(c)(i) (1 mark): The student adds an excess of aqueous ammonia to their aqueous solution of Tutton’s salt. A deep blue solution forms. The complex ion responsible for the deep b
  22. June 2022, Paper 1, Q15 (1 mark): Which ion(s) contain(s) one or more unpaired electrons? Mn3+ 1 V3+ 2 Cu+ 3 A 1, 2 and 3 B Only 1 and 2 C Only 2 and 3 D Only 1 Your answer [1]
  23. June 2022, Paper 1, Q22(a)(i) (1 mark): Explain why ethane-1,2-diamine can act as a bidentate ligand. [1]
  24. June 2022, Paper 1, Q22(a)(ii) (4 marks): The iron(III) ion, Fe3+, forms a complex ion A with two ethane-1,2-diamine ligands and two chloride ligands. Complex ion A has cis and trans stereoisomers. One
  25. June 2022, Paper 1, Q22(b)(i) (1 mark): Write an ionic equation for the formation of the pale green precipitate. [1]
  26. June 2022, Paper 1, Q22(c) (6 marks): This question is about reactions of transition metal compounds. (c)* This question is about copper and copper compounds. Experiment 1 Hydrochloric acid, HCl (aq
  27. June 2022, Paper 3, Q1(d)(ii) (3 marks): Glycine reacts with aqueous copper(II) ethanoate to form copper(II) glycinate, Cu(H2NCH2COO)2, and ethanoic acid. Copper(II) glycinate is a complex which exists
  28. November 2021, Paper 1, Q17(a) (4 marks): Most d-block elements are also classified as transition elements. Explain why scandium and zinc are classified as d-block elements but are not also transition e
  29. November 2021, Paper 1, Q17(b)(i) (1 mark): What is meant by a bidentate ligand? [1]
  30. November 2021, Paper 1, Q17(b)(ii) (6 marks): This question is about d-block elements. (ii)* Determine the formulae of A and B. Write the ionic equation for the ligand substitution and show 3D structures fo
  31. November 2021, Paper 1, Q18(b) (1 mark): Write an ionic equation, including state symbols, for the reaction in Step 3. [1]
  32. November 2020, Paper 1, Q5 (1 mark): Which statement about elements in the d block of Period 4 of the periodic table is correct? Cr atoms have the electron configuration: 1s22s22p63s23p63d54s1. A C
  33. November 2020, Paper 1, Q15 (1 mark): Which statement(s) for the complex ion [Co(NH2CH2CH2NH2)3]2+ is/are correct? 1 It has cis and trans isomers. 2 It has optical isomers. 3 It is six-fold coordina
  34. November 2020, Paper 1, Q22(a) (6 marks): (a)* B and C are compounds of two different transition elements. A student carries out test tube reactions on aqueous solutions of B and C. The observations of
  35. November 2020, Paper 3, Q2 (6 marks): 2* Transition metal ions can bond to ligands to form complex ions with different shapes. Explain what is meant by the terms ligand, coordination number and liga
  36. June 2019, Paper 1, Q13 (1 mark): What is the number of stereoisomers that Ni(H2NCH2CH2NH2)2Cl 2 can form? A 2 B 3 C 4 D 6 Your answer [1]
  37. June 2019, Paper 1, Q14 (1 mark): Which property/properties is/are correct for a transition element? 1 The element has atoms with a partially filled d sub-shell. 2 The existence of more than one
  38. June 2019, Paper 1, Q17(b) (3 marks): Red blood cells contain haemoglobin. Explain using ligand substitutions: • how haemoglobin transports oxygen around the body • why carbon monoxide is toxic. [3]
  39. June 2019, Paper 1, Q18(a)(i) (1 mark): What is the formula of the complex ion in the purple solution that forms in Experiment 1? [1]
  40. June 2019, Paper 1, Q18(a)(ii) (1 mark): Suggest an equation for the reaction in Experiment 2, Step 1. Include state symbols. [1]
  41. June 2019, Paper 1, Q18(a)(iii) (2 marks): Draw a 3-D diagram for the shape of the complex ion that forms in Experiment 2, Step 2. Include the charge of the ion. [2]
  42. June 2019, Paper 1, Q18(a)(iv) (1 mark): What is the formula of the ion that causes the yellow colour in Experiment 2, Step 3? [1]
  43. June 2019, Paper 1, Q18(a)(v) (1 mark): State the colour of the solution that forms in Experiment 2, Step 4. [1]
  44. June 2019, Paper 1, Q18(b)(i) (1 mark): Complete the electron configuration of a V3+ ion. 1s2 [1]
  45. June 2019, Paper 3, Q6(a)(i) (2 marks): In the boxes, write the formulae of A and B. [2]
  46. June 2019, Paper 3, Q6(a)(iii) (1 mark): Write the equation for the reaction of [Fe(H2O)6]2+(aq) with Cl 2(g). [1]
  47. June 2018, Paper 1, Q15 (1 mark): Which statement(s) is/are correct for the complex Pt(NH3)2Cl2? 1 One of its stereoisomers is used as an anti-cancer drug. 2 It has bond angles of 109.5°. 3 It h
  48. June 2018, Paper 1, Q21(a) (2 marks): Complete the electron configuration of a Ni atom: 1s2 a Ni2+ ion: 1s2 [2]
  49. June 2018, Paper 3, Q2(c)(i) (1 mark): Write the equilibrium equation for the reaction that takes place when the colour of the solution changes. [1]
  50. June 2018, Paper 3, Q3(a) (3 marks): The ethanedioate ion, shown below, can act as a bidentate ligand. O O –O O– Fe3+ forms a complex ion with three ethanedioate ions. The complex ion has two optic
  51. June 2018, Paper 3, Q4(a)(ii) (2 marks): Cis-platin is prepared in a ligand substitution reaction which takes place in multiple steps. The equation for the final step forming cis-platin is shown below.
  52. June 2017, Paper 1, Q2 (1 mark): What is the bonding between the ligands and the metal ion in [Fe(H2O)6]2+? 2 A Metallic B Ionic C Hydrogen D Dative covalent Your answer [1]
  53. June 2017, Paper 1, Q11 (1 mark): Aqueous Cr3+ ions are reacted with an excess of aqueous sodium hydroxide. Which product is formed? 3– A Cr(OH)6 B Cr(OH)3 [Cr(OH)4(H2O)2]– C [Cr(OH)4]3– D Your
  54. June 2017, Paper 1, Q15 (1 mark): Which electron configuration(s) is/are correct? Cr atom: 1s22s22p63s23p63d54s1 1 Cu atom: 1s22s22p63s23p63d104s1 2 Fe2+ ion: 1s22s22p63s23p63d54s1 3 A 1, 2 and
  55. June 2017, Paper 1, Q23(a)(i) (5 marks): In the boxes, write down the formulae of the species responsible for the observations. yellow solution Reaction 1 HCl(aq) NH3(aq) [Cu(H2O)6]2+ pale blue solutio
  56. June 2017, Paper 1, Q23(a)(ii) (2 marks): Name the type of reaction for Reaction 1 and Reaction 2. Reaction 1 Reaction 2 [2]
  57. June 2017, Paper 1, Q23(b) (6 marks): This question is about reactions of ions and compounds of transition elements. (b)* A hydrated nickel(II) complex, A, is heated in a crucible to remove the wate
  58. June 2017, Paper 3, Q4(c)(i) (1 mark): Draw the structure of the ligand in chromium(III) picolinate. [1]

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