Question

Which of the following is a correct increasing order of ligand field strength ?

• A. \(\text{EDTA} < \text{C}_2\text{O}_4^{2-} < \text{H}_2\text{O} < \text{en}\)
• B. \(\text{en} < \text{H}_2\text{O} < \text{EDTA} < \text{C}_2\text{O}_4^{2-}\)
• C. \(\text{C}_2\text{O}_4^{2-} < \text{H}_2\text{O} < \text{EDTA} < \text{en}\)
• D. \(\text{H}_2\text{O} < \text{en} < \text{C}_2\text{O}_4^{2-} < \text{EDTA}\)

Hint:

Spectrochemical series order here: oxalate < water < EDTA < en.

Answer 1

The Correct Option is C

Step 1: Recall where each ligand sits:
Oxalate sits below water in the series ($\text{C}_2\text{O}_4^{2-} < \text{H}_2\text{O}$). Water is below the nitrogen-donor chelators. EDTA is below ethylenediamine. So the order is oxalate, water, EDTA, en.

Step 2: Test the options:
(A): starts with EDTA, but EDTA is stronger than water, so this is reversed.
(B): puts en at the weak end, but en has the strongest field of the four.
(D): puts water first, yet oxalate is weaker than water.
(C): gives the correct sequence.

Final Answer:
Option (C). \[ \boxed{\text{C}_2\text{O}_4^{2-}<\text{H}_2\text{O}<\text{EDTA}<\text{en} \text{ (C)}} \]