Stability constants, Kstab: past paper questions

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• Question 6May/June 2026, paper 41Structured8 marks

  Transition elements form complexes with species called ligands. The ethanedioate ion, ${\text{C}}_2{\text{O}}_4^{2-}$, is a bidentate ligand. Explain what is meant by bidentate ligand.

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• Question 6Oct/Nov 2025, paper 42Structured7 marks

  Nickel forms complexes. Give the formula and charge of the tetrahedral complex formed by $\mathrm{N}\mathrm{i}$ atoms with carbon monoxide molecules.

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• Question 4Oct/Nov 2024, paper 41Structured12 marks

  Transition metal atoms and transition metal ions form complexes by combining with ligands. Explain why transition elements form complex ions.

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• Question 5Oct/Nov 2023, paper 41Structured12 marks

  Transition elements behave as catalysts and can form complex ions. Explain why transition elements behave as catalysts.

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• Question 5Oct/Nov 2024, paper 42Structured6 marksHas a diagram

  ${\text{Ni}}^{2+}$ ions form a number of different complex ions, including $[\text{Ni}({\text{H}}_2\text{O}{)}_6{]}^{2+}$, $[\text{Ni}({\text{NH}}_3{)}_6{]}^{2+}$ and $[\text{Ni}(\text{en}{)}_3{]}^{2+}$. The abbreviation en represents 1,2-diaminoethane.

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• Question 1May/June 2023, paper 41Structured19 marksHas a diagram

  Group 2 nitrates decompose when heated. Describe how the thermal stability of Group 2 nitrates changes with increasing proton number.

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