Complex ions and ligandsEdexcel A-Level Chemistry: Mind map

Exam questions on Complex ions and ligands

1. A student dissolves iron(II) sulfate in water. The iron(II) ions are present as the pale green complex ion [Fe(H₂O)₆]²⁺.
   Explain why water acts as a monodentate ligand.2 marks
2. Cis-platin, Pt(NH₃)₂Cl₂, is a square planar complex used in chemotherapy. Its isomer, trans-platin, has the same formula but is not used as a drug.
   Explain why cis-platin is supplied for cancer treatment as a single isomer rather than as a mixture with trans-platin.2 marks
3. Nickel(II) ions form the green complex ion [Ni(H₂O)₆]²⁺ in water. Chemists can replace the water ligands with ethane-1,2-diamine, NH₂CH₂CH₂NH₂ (en), or with the ethylenediaminetetraacetate ion, EDTA⁴⁻.
   Ethane-1,2-diamine is a bidentate ligand and forms the complex ion [Ni(NH₂CH₂CH₂NH₂)₃]²⁺. Explain what is meant by bidentate and deduce the coordination number of nickel in this complex.3 marks