Medium MCQ +4 / -1 PYQ · JEE Mains 2020

[Pd(F)(Cl)(Br)(I)]2– has n number of geometrical isomers. Then, the spin-only magnetic moment and crystal field stabilisation energy [CFSE] of [Fe(CN)6]n–6, respectively, are:
[Note : Ignore the pairing energy]

  1. A 1.73 BM and –2.0 $\Delta$<sub>0</sub> Correct answer
  2. B 5.92 BM and 0
  3. C 2.84 BM and –1.6 $\Delta$<sub>0</sub>
  4. D 0 BM and –2.4 $\Delta$<sub>0</sub>

Solution

Complex [Pd(F)(Cl)(Br)(I)]<sup>2–</sup> (square planar geometry)-has 3 geometrical isomers. <br><br>$\therefore$ n = 3 <br><br>[Fe(CN)<sub>6</sub>]<sup>n–6</sup> becomes [Fe(CN)<sub>6</sub>]<sup>3-</sup> <br><br>Here Oxidation state of Fe = +3 <br><br>$\therefore$ Fe<sup>+3</sup> = [Ar]3d<sup>5</sup>4s<sup>0</sup> <br><br>CN<sup>-</sup> is strong field ligand so it pairing of electrons happens. <br><br>E.C. according to CFT = ($t_{2g}^5e{g^0}$) <br><br>$\therefore$ No. of unpaired e<sup>-</sup> = 1 <br><br>Then Magnetic moment = $\sqrt {n\left( {n + 2} \right)}$ = $\sqrt 3$ = 1.73 B.M <br><br>CFSE = [(–0.4 × 5) + (0.6 × 0)] $\Delta$<sub>0</sub> = –2.0 $\Delta$<sub>0</sub>

About this question

Subject: Chemistry · Chapter: Coordination Compounds · Topic: Ligands and Coordination Number

This question is part of PrepWiser's free JEE Main question bank. 173 more solved questions on Coordination Compounds are available — start with the harder ones if your accuracy is >70%.

Drill 25 more like these. Every day. Free.

PrepWiser turns these solved questions into a daily practice loop. Chapter-wise drills, full mocks, AI doubt chat. No auto-renew.

Start free →