Question

The crystal field stabilization energy (CFSE) of [Fe(H₂O)₆]Cl₂ and K₂[NiCl₄] respectively, are ______.

Options

• −0.4 Δ_o and −0.8 Δ_t

• −0.6 Δ_o and −0.8 Δ_t

• −2.4 Δ_o and −1.2 Δ_t

• −0.4 Δ_o and −1.2 Δ_t

Answer 1

The crystal field stabilization energy (CFSE) of [Fe(H₂O)₆]Cl₂ and K₂[NiCl₄] respectively, are `bbunderline(-0.4 Δ_o and -0.8 Δ_t)`.

Explanation:

The Crystal Field Stabilisation Energy (CFSE) is calculated as the energy of the electron configuration in the ligand field minus the energy of the electronic configuration in the isotropic field.

CFSE is determined by the given formula

CFSE = ΔE = `E_"ligand field" – E_"isotropic field"`

For [Fe(H₂O)₆]Cl₂:

\[\ce{Fe^{2+} -> [Ar] 3d^6 -> (t_{2g})^4 (e_g)^2}\]

H₂O is a weak field ligand, hence pairing is not possible.

C.F.S.E. = 4 × (−0.4 Δ_o) + 2 × 0.6 Δ_o

= −1.6 Δ_o + 1.2 Δ_o

∴ C.F.S.E. = −0.4 Δ_o

For K₂[NiCl₄]:

\[\ce{K_2[NiCl_4], Ni^{2+} -> [Ar] 3d^8 -> (e_g)^4 (t_{2g})^4}\]

Cl⁻ Weak field ligands lack Δ_o pairing and have a tetrahedral shape.

C.F.S.E. = 4 × (−0.6 Δ_t) + 4 × 0.4 Δ_t

= −2.4 Δ_t + 1.6 Δ_t

∴ C.F.S.E. = −0.8 Δ_t

Thus, the required CFSE are −0.4 Δ_o and −0.8 Δ_t.