(a) Iron forms complex ions with the monodentate ligand, CN¯.

1. (a)(i)Complex ion A contains one Fe3+ ion and six CN- ligands. Complex ion B contains one Fe2+ ion and six CN¯ ligands. State the formulae of these two complex ions. Include the overall charge of each complex ion. complex ion A complex ion B[1]
2. (a)(ii)Explain why a solution containing complex ion A and a solution containing complex ion B are different colours.[2]
3. (a)(iii)In complex ion A, the carbon atom of each CN¯ ligand bonds to the Fe3+ ion. State the type of bonding involved.[1]
4. (b)Complex ions have different geometries. Complex ion A is octahedral. Ag+ ions form a linear complex with ammonia. Ni atoms form a tetrahedral complex with carbon monoxide molecules. The carbon atom in the monodentate carbon monoxide ligand bonds to the nickel atom. Pd2+ ions form a square planar complex with chloride ions. Complete Fig. 6.1 to show the geometry of each of these four ions, using three-dimensional bonds where necessary. Label one bond angle on each complex ion. [Figure 6.1][4]

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