Exams › JEE Main › Chemistry

The correct order of the spin-only magnetic moments of the following complexes is : (I) [Cr(H2O)6]Br2 (II) Na4[Fe(CN)6] (III) Na3[Fe(C2O4)3](Δo > P) (IV) (Et4N)2 [CoCl4]

1. (I) > (IV) > (III) > (II)
2. (II) ≈ (I) > (IV) > (III)
3. (III) > (I) > (IV) > (II)
4. (III) > (I) > (II) > (IV)

Correct answer: (I) > (IV) > (III) > (II)

Solution

The correct order reflects the number of unpaired electrons in each complex, which determines the spin-only magnetic moment. [Cr(H2O)6]Br2 has the highest number of unpaired electrons due to its high-spin configuration, followed by (Et4N)2[CoCl4], which has fewer unpaired electrons, while Na3[Fe(C2O4)3] has a low-spin configuration with the least unpaired electrons, and Na4[Fe(CN)6] is fully paired, resulting in no magnetic moment.

Related JEE Main Chemistry questions

• When sodium hydroxide is introduced into an aqueous Zn2+ solution, a white precipitate forms, and this precipitate dissolves when more NaOH is added. In such a solution, zinc is present in the:
• When excess ammonia is added to a copper sulphate solution, a deep blue colour appears because of the formation of which species?
• In the nitroprusside ion, iron and NO are present as Fe$^{2+}$ and NO$^+$ instead of Fe$^{3+}$ and NO. These two formulations can be distinguished by
• In the brown ring test for nitrite and nitrate ions, the characteristic brown ring is produced because a complex ion is formed with which formula?
• What is the spin-only magnetic moment, expressed in Bohr magnetons (μB), for Ni²⁺ in aqueous solution? (Atomic number of Ni = 28)
• Silver chloride dissolves in aqueous ammonium hydroxide because it leads to the formation of which species?

⚔️ Practice JEE Main Chemistry free + battle 1v1 →