Q82 / 180 · NEET 2026 (Re-NEET) · Chemistry
According to crystal field theory, the correct order of ligands with respect to their decreasing order of field strength is
- A$\text{Cl}^->\text{NH}_3>\text{H}_2\text{O}>\text{CO}$
- Correct answerB$\text{CO}>\text{NH}_3>\text{H}_2\text{O}>\text{Cl}^-$
- C$\text{CO}>\text{H}_2\text{O}>\text{NH}_3>\text{Cl}^-$
- D$\text{Cl}^->\text{H}_2\text{O}>\text{NH}_3>\text{CO}$
Solution
According to the spectrochemical series, the arrangement of ligands in the increasing order of their crystal field splitting energy (CFSE) or field strength is:
$\text{I}^- < \text{Br}^- < \text{SCN}^- < \text{Cl}^- < \text{S}^{2-} < \text{F}^- < \text{OH}^- < \text{C}_2\text{O}_4^{2-} < \text{H}_2\text{O} < \text{NCS}^- < \text{edta}^{4-} < \text{NH}_3 < \text{en} < \text{CN}^- < \text{CO}$
From the given ligands, the decreasing order of field strength is:
$\text{CO} > \text{NH}_3 > \text{H}_2\text{O} > \text{Cl}^-$
Answer: $\text{CO}>\text{NH}_3>\text{H}_2\text{O}>\text{Cl}^-$
$\text{I}^- < \text{Br}^- < \text{SCN}^- < \text{Cl}^- < \text{S}^{2-} < \text{F}^- < \text{OH}^- < \text{C}_2\text{O}_4^{2-} < \text{H}_2\text{O} < \text{NCS}^- < \text{edta}^{4-} < \text{NH}_3 < \text{en} < \text{CN}^- < \text{CO}$
From the given ligands, the decreasing order of field strength is:
$\text{CO} > \text{NH}_3 > \text{H}_2\text{O} > \text{Cl}^-$
Answer: $\text{CO}>\text{NH}_3>\text{H}_2\text{O}>\text{Cl}^-$
Hence, the correct answer is option: 'B'.