JEE Main 2026 — Jan 21, Shift 2 — Chemistry solution

JEE Main2026Jan 21, Shift 2Chemistry

Given below are two statements:

Statement I: Crystal Field Stabilization Energy (CFSE) of $[C r (H_{2} O)_{6}]^{2 +}$ is greater than that of $[M n (H_{2} O)_{6}]^{2 +}$ .

Statement II: Potassium ferricyanide has a greater spin-only magnetic moment than sodium Ferrocyanide.

In the light of the above statements, choose the correct answer from the options given below:

A
Both Statement I and Statement II are true
B
Both Statement I and Statement II are false
C
Statement I is true but Statement II is false
D
Statement I is false but Statement II is true

Solution

Statement I: $M n^{2 +}$ is $d^{5}$ high-spin in a weak-field aquo environment, giving CFSE = 0. $C r^{2 +}$ is $d^{4}$ high-spin, giving CFSE = $- 0.6 Δ_{0}$ . So $∣ C F S E ∣$ for the Cr complex is greater. True.

Statement II: $K_{3} [F e (C N)_{6}]$ has Fe $^{3 +}$ ( $d^{5}$ , low spin with strong-field CN $^{-}$ ): one unpaired electron, $μ = 1 (1 + 2) = 3$ B.M. $N a_{4} [F e (C N)_{6}]$ has Fe $^{2 +}$ ( $d^{6}$ , low spin): zero unpaired electrons, $μ = 0$ . So ferricyanide has the larger magnetic moment. True.

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