Q20. The pair in which both the species have the same magnetic moment (spin only value) is:
(a) [Cr(H2O)6]2+, [CoCl4]2-
(b) [Cr(H2O)6]2+, [Fe(H2O)6]2+
(c) [Mn(H2O)6]2+, [Cr(H2O)6]2+
(d) [CoCl4]2-, [Fe

Question

Q20. The pair in which both the species have the same magnetic moment (spin only value) is:
(a) [Cr(H2O)6]2+, [CoCl4]2-
(b) [Cr(H2O)6]2+, [Fe(H2O)6]2+
(c) [Mn(H2O)6]2+, [Cr(H2O)6]2+
(d) [CoCl4]2-, [Fe(H2O)6]2+

FirstInTest · Accepted Answer

Correct answer: b. [Cr(H2O)6]2+ and [Fe(H2O)6]2+ have same magnetic moment as both Cr2+ and Fe2+ have same number of unpaired electrons.Cr2+: [Ar]3d4, H2O is a weak field ligand, so high spin. 4 unpaired electrons.Fe2+: [Ar]3d6, H2O is a weak field ligand, so high spin. 4 unpaired electrons.Since both have 4 unpaired electrons, their spin-only magnetic moment (μ = √n(n+2)) will be the same.

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