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Question:

The correct statement about the magnetic properties of [Fe(CN)6]³⁻ and [FeF6]³⁻ is (Z=26):

[Fe(CN)6]³⁻ is paramagnetic, [FeF6]³⁻ is diamagnetic.

Both are diamagnetic.

Both are paramagnetic.

[Fe(CN)6]³⁻ is diamagnetic, [FeF6]³⁻ is paramagnetic.

Solution:

The oxidation number of Fe in [Fe(CN)6]³⁻ and [FeF6]³⁻ is +3. The electronic configuration of Fe³⁺ is [Ar]3d⁵. In [FeF6]³⁻, F⁻ is a weak field ligand, resulting in high spin complex with 5 unpaired electrons. In [Fe(CN)6]³⁻, CN⁻ is a strong field ligand, resulting in a low spin complex with only 1 unpaired electron. Therefore, [FeF6]³⁻ is paramagnetic due to 5 unpaired electrons, and [Fe(CN)6]³⁻ is paramagnetic due to 1 unpaired electron. The correct statement is that [Fe(CN)6]³⁻ is paramagnetic, and [FeF6]³⁻ is paramagnetic.