AIIMS2019Chemistry-Coordination Compounds

AIIMS 2019 Chemistry Magnetic Properties MCQ Question

Type: MCQ-conceptual-Medium-Class 12

Assertion : Potassium ferricyanide, [Fe(CN)6]3[\text{Fe}(\text{CN})_6]^{3-} is diamagnetic, while potassium ferrocyanide [Fe(CN)6]4[\text{Fe}(\text{CN})_6]^{4-} is paramagnetic.Reason : Oxidation state of Fe\text{Fe} in potassium ferricyanide is +2, but in potassium ferrocyanide its oxidation state is +3.

A

If both assertion and reason are true and reason is correct explanation of assertion.

B

If both assertion and reason are true and reason is not correct explanation of assertion.

C

If assertion is true but reason is false.

D

If assertion is true but reason is false.

Correct Answer

Option D

Detailed Explanation

The statement regarding K₃[Fe(CN)₆] being slightly paramagnetic due to its oxidation state (O.S.) of +3 is accurate, as it contains unpaired electrons in the d-orbitals of Fe³⁺. However, the assertion about K₄[Fe(CN)₆] being diamagnetic with an O.S. of +2 is misleading because it does not account for the electronic configuration of the iron ion in this complex, which is actually Fe²⁺ and can exhibit unpaired electrons depending on the ligand field. Therefore, the overall characterization of both complexes is not entirely correct, leading to the conclusion that option D is appropriate. Options A and B are incorrect as they oversimplify the magnetic properties of these complexes, while option C is not applicable since the information provided allows for a definitive assessment.

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