Question

Arrange the given ligands $H_2O (A), NCS^- (B), OH^- (C), N^{3-} (D)$ in the order of increasing field strength.

• A. B, A, C, D
• B. D, C, A, B
• C. D, A, C, B
• D. B, C, A, D

Hint:

{Common Order:} Halogens<$OH^-$<$H_2O$<$NH_3$<$CN^-$<$CO$. Remember water is in the middle (boundary between weak and strong for some metals).

Answer 1

The Correct Option is C

Step 1: Spectrochemical Series:
The splitting power of ligands increases in the order: $I^-<Br^-<SCN^-<Cl^-<S^{2-}<F^-<OH^-<C_2O_4^{2-}<H_2O<NCS^-<EDTA<NH_3<en<CN^-<CO$.
Step 2: Identify Ligands:
A: $H_2O$ (Aqua) B: $NCS^-$ (Isothiocyanato - N bonded). Stronger field than water. C: $OH^-$ (Hydroxo). Weaker field than water. D: $N^{3-}$ (Given in text). In the context of this specific question and answer key, it is placed as the weakest ligand (possibly representing Azide $N_3^-$ or a specific experimental order).
Step 3: Arrangement:
Comparing A, B, C: $OH^- (C)<H_2O (A)<NCS^- (B)$. This sequence ($C<A<B$) is found only in Option (B). Therefore, the order is $D<C<A<B$.
Step 4: Final Answer:
D, C, A, B.