The octahedral splitting o of [Cr(H 2O) 6]3+, [CrF 6]3- and [Cr(CN) 6]3- follows .

$[Cr(H_2O)_6]^{3+}>[CrF_6]^{3-}>[Cr(CN)_6]^{3-}$

$[CrF_6]^{3-}>[Cr(H_2O)_6]^{3+}>[Cr(CN)_6]^{3-}$

$[CrF_6]^{3-}>[Cr(CN)_6]^{3-}>[Cr(H_2O)_6]^{3+}$

GATE 2021 CY – Question 24

Inorganic Chemistry · Transition Metals: Coordination chemistry – structure and isomerism, theories of bonding (VBT, CFT, and MOT). Metal-metal multiple bonds. Energy level diagrams in various crystal fields, CFSE, applications of CFT, Jahn-Teller distortion. Electronic spectra of transition metal complexes: spectroscopic term symbols, selection rules, Orgel and Tanabe-Sugano diagrams, nephelauxetic effect and Racah parameter, charge-transfer spectra. Magnetic properties of transition metal complexes. Ray-Dutt and Bailar twists, Reaction mechanisms: kinetic and thermodynamic stability, associative, dissociative substitution and redox reactions. · 1 mark · Multiple choice

The octahedral splitting $\Delta_o$ of $[Cr(H_2O)_6]^{3+}$, $[CrF_6]^{3-}$ and $[Cr(CN)_6]^{3-}$ follows ______.

$[Cr(H_2O)_6]^{3+}>[CrF_6]^{3-}>[Cr(CN)_6]^{3-}$
$[CrF_6]^{3-}>[Cr(H_2O)_6]^{3+}>[Cr(CN)_6]^{3-}$
$[Cr(CN)_6]^{3-}>[Cr(H_2O)_6]^{3+}>[CrF_6]^{3-}$
$[CrF_6]^{3-}>[Cr(CN)_6]^{3-}>[Cr(H_2O)_6]^{3+}$

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Correct answer: (C) $[Cr(CN)_6]^{3-}>[Cr(H_2O)_6]^{3+}>[CrF_6]^{3-}$

Explanation

The metal and its oxidation state remain Cr(III), so ligand-field strength determines the order. In the spectrochemical series, F− is weaker field than H2O, while CN− is substantially stronger field.

Thus **Δo(CN−)>Δo(H2O)>Δo(F−), C**.