Explanation

Statement I :

In both complexes, H₂O is a weak field ligand, so octahedral complexes formed are high spin.

For [Cr(H₂O)₆]²⁺ :

Cr²⁺ → 3d⁴ configuration

High spin octahedral → t_2g³ e_g¹

CFSE = (−0.4 × 3 + 0.6 × 1)Δ₀

= (−1.2 + 0.6)Δ₀

= −0.6Δ₀

For [Mn(H₂O)₆]²⁺ :

Mn²⁺ → 3d⁵ configuration

High spin octahedral → t_2g³ e_g²

CFSE = (−0.4 × 3 + 0.6 × 2)Δ₀

= (−1.2 + 1.2)Δ₀

= 0

Thus, CFSE of Cr²⁺ complex is greater than Mn²⁺ complex.

Statement I is true.

Statement II :

Potassium ferricyanide → K₃[Fe(CN)₆]

Fe³⁺ → 3d⁵

CN⁻ is strong field ligand → low spin configuration

t_2g⁵ e_g⁰

Unpaired electrons = 1

Sodium ferrocyanide → Na₄[Fe(CN)₆]

Fe²⁺ → 3d⁶

Low spin configuration → t_2g⁶ e_g⁰

Unpaired electrons = 0

Spin-only magnetic moment depends on number of unpaired electrons.

Ferricyanide (1 unpaired electron) has greater magnetic moment than ferrocyanide (0 unpaired electrons).

Statement II is true.

Therefore, both Statement I and Statement II are true.

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