Question

Find the correct match.

Column-I (Complex compound)	Column-II ($\Delta_0$ (CFSE) $\text{cm}^{-1}$)
(i) $[Cr(CN)_6]^{3-}$	(P) 17000
(ii) $[Cr(H_2O)_6]^{3+}$	(Q) 15000
(iii) $[Cr(en)_3]^{3+}$	(R) 12000
(iv) $[CrF_6]^{3-}$	(S) 20000

• (A) (i) → P ; (ii) → Q ; (iii) → S ; (iv) → R
• (B) (i) → S ; (ii) → Q ; (iii) → P ; (iv) → R
• (C) (i) → R ; (ii) → P ; (iii) → Q ; (iv) → S
• (D) (i) → P ; (ii) → R ; (iii) → Q ; (iv) → S

Answer 1

The Correct Option is B

Correlation between ligand field strength and Crystal Field Splitting energy ($\Delta_0$).

LOGIC:
1. CFSE ($\Delta_0$) $\propto$ strength of the ligand.
2. From spectrochemical series: $CN^-$ (Strong) $> en > H_2O > F^-$ (Weak).
3. Thus, the highest $\Delta_0$ (20000) belongs to the $CN^-$ complex (i-S).
4. The second highest (17000) belongs to the ethylenediamine complex (iii-P).
5. The third (15000) belongs to the water complex (ii-Q).
6. The lowest (12000) belongs to the fluoride complex (iv-R).
7. The set is: (i)-S, (ii)-Q, (iii)-P, (iv)-R. Option (B) matches this.