The extent of Mossbauer quadrupole splitting of iron follows the order · ABC26IN0417

Subject: Inorganic Chemistry · Chapter: Inorganic Spectroscopy · Topic: Inorganic Spectroscopy – General · Exam: GATE 2005-2021 · Marks: 2 · Difficulty: Easy

The extent of Mossbauer quadrupole splitting of iron follows the order
(a)$\mathrm{FeCl}_{2} \cdot 4 \mathrm{H}_{2} \mathrm{O}>\mathrm{K}_{2}\left[\mathrm{Fe}(\mathrm{CN})_{5}(\mathrm{NO})\right]>\mathrm{FeCl}_{3} \cdot 6 \mathrm{H}_{2} \mathrm{O}$
(b)$\mathrm{K}_{2}\left[\mathrm{Fe}(\mathrm{CN})_{5}(\mathrm{NO})\right]<\mathrm{FeCl}_{2} \cdot 4 \mathrm{H}_{2} \mathrm{O}>\mathrm{FeCl}_{3} \cdot 6 \mathrm{H}_{2} \mathrm{O}$
(c)$\mathrm{FeCl}_{3} \cdot 6 \mathrm{H}_{2} \mathrm{O}>\mathrm{K}_{2}\left[\mathrm{Fe}(\mathrm{CN})_{5}(\mathrm{NO})\right]>\mathrm{FeCl}_{2} \cdot 4 \mathrm{H}_{2} \mathrm{O}$
(d)$\mathrm{FeCl}_{2} \cdot 4 \mathrm{H}_{2} \mathrm{O}>\mathrm{FeCl}_{3} \cdot 6 \mathrm{H}_{2} \mathrm{O}>\mathrm{K}_{2}\left[\mathrm{Fe}(\mathrm{CN})_{5}(\mathrm{NO})\right]$
Answer
Answer: A ✓ checked by 4AB · confidence medium
Explanation
High-spin Fe(II) (FeCl₂·4H₂O) has an asymmetric d⁶ shell and a large quadrupole splitting (~3 mm s⁻¹). Nitroprusside, with a strongly asymmetric ligand set, shows ~1.7. High-spin Fe(III) (d⁵, spherical) shows a small splitting (a).

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