Question 33 of 34intermediate🔍 AnalyzeMCQ1 mark

Amongst the following, the most stable complex is

Exercise: EXERCISES | Q: 5.30 | (Page Page 23)
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Explanation

The correct answer is option (iii) [Fe(C2O4)3]3-. Among the given complexes, oxalate (C2O4)2- is a bidentate ligand that forms chelate rings with the metal ion. Chelate complexes are significantly more stable than complexes formed with monodentate ligands like H2O, NH3, and Cl- due to the chelate effect. The other options (i), (ii), and (iv) all contain monodentate ligands. The context mentions that complex ions like [Fe(CN)6]4- do not dissociate into simple ions, indicating the stability of coordination complexes. Additionally, the context discusses inner orbital complexes being more stable, and chelating ligands generally enhance complex stability through ring formation.

Solution Steps

  1. Step 1: Identify the nature of ligands in each complex - H2O, NH3, and Cl- are monodentate ligands, while C2O4(2-) (oxalate) is a bidentate ligand.

  2. Step 2: Apply the chelate effect principle - bidentate/polydentate ligands form more stable complexes than monodentate ligands due to ring formation (chelation).

  3. Step 3: Conclude that [Fe(C2O4)3]3- is the most stable complex among the given options because it contains a bidentate ligand forming chelate rings.

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