The correct order of the wavelength of light absorbed by the following complexes is, A. [ Co ( NH 3 ) 6 ] 3+ B. [ Co ( CN ) 6 ] 3- C. [ Cu ( H 2 O ) 4 ] 2+ D. [ Ti ( H 2 O ) 6 ] 3+ Choose the correct answer from the options given below:

Chemistry · Coordination Compounds

NEET (UG) 2025 — Question 53

The correct order of the wavelength of light absorbed by the following complexes is,

A. $\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{6}\right]^{3+}$

B. $\left[\mathrm{Co}(\mathrm{CN})_{6}\right]^{3-}$

C. $\left[\mathrm{Cu}\left(\mathrm{H}_{2} \mathrm{O}\right)_{4}\right]^{2+}$

D. $\left[\mathrm{Ti}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{3+}$

Choose the correct answer from the options given below:

Option A:
B $<$ D $<$ A $<$ C
Option B:
B $<$ A $<$ D $<$ C
Correct
Option C:
C $<$ D $<$ A $<$ B
Option D:
C $<$ A $<$ D $<$ B

Answer: B

Step-by-step solution

The wavelength of light absorbed is inversely related to the crystal field splitting energy (Δ₀). Stronger field ligands cause larger Δ₀, higher energy absorption, and thus shorter wavelength. For the complexes: [Co(CN)₆]³⁻ has CN⁻ (strong field ligand) → largest Δ₀ → shortest λ. [Co(NH₃)₆]³⁺ has NH₃ (moderate field) → intermediate Δ₀. [Ti(H₂O)₆]³⁺ has H₂O (weak field) and Ti³⁺ (d¹) → small Δ₀. [Cu(H₂O)₄]²⁺ has H₂O (weak field) and Cu²⁺ (d⁹, Jahn-Teller distortion) → smallest Δ₀ → longest λ. Thus the order of increasing λ (longest to shortest) is: C (Cu complex) > D (Ti complex) > A (Co-NH₃ complex) > B (Co-CN complex). Therefore the correct order of wavelength absorbed is B < A < D < C, which corresponds to option B.

Answer key and solution verified before publishing.

Practise Coordination Compounds

Start with this question, then two more from the same chapter — with a tutor that explains every step. Free.

Solve a similar one free

Exam: NEET (UG) 2025
Paper: 2025 paper
Subject: Chemistry
Chapter: Coordination Compounds
Topic: Properties and importance of Coordination Complexes

Answer: B

Step-by-step solution

Practise Coordination Compounds

More Coordination Compounds questions from this paper