The correct order of the complexes $\mathrm{[Co(NH_3)_5(H_2O)]^{3+}}$ (A), $\mathrm{[Co(NH_3)_6]^{3+}}$ (B), $\mathrm{[Co(CN)_6]^{3-}}$ (C) and $\mathrm{[CoCl(NH_3)_5]^{2+}}$ (D) in terms of wavelength of light absorbed is

JEE Main 2025 · ChemistryMultiple choiceSingle correctMediumApplication

JEE Main 3 April 2025, Shift 1, Chemistry Q63

Question 63 of 75 in this shift, Chemistry question 13 of 25, Section A.

The correct order of the complexes

\mathrm{[Co(NH_3)_5(H_2O)]^{3+}}

(A),

\mathrm{[Co(NH_3)_6]^{3+}}

(B),

\mathrm{[Co(CN)_6]^{3-}}

\mathrm{[CoCl(NH_3)_5]^{2+}}

(D) in terms of wavelength of light absorbed is

(1)C > B > A > D
(2)C > B > D > A
(3)D > C > B > A
(4)D > A > B > COfficial answer

Official answer

Option 4

NTA final key.

Chapter: Coordination Compounds
Topic: Crystal Field Theory
Idea tested: Color and d-d Transitions

Same idea in other shifts

Asked 3× in all

25 Jul 2022, Shift 1 · Q86Consider the following metal complexes : $[\mathrm{Co(NH_3)_6}]^{3+}$ $[\mathrm{CoCl(NH_3)_5}]^{2+}$ $[\mathrm{Co(CN)_6}]^{3-}$ …MediumNumerical value
16 Mar 2021, Shift 2 · Q59 $\mathrm{[Ti(H_2O)_6]^{3+}}$ absorbs light of wavelength 498 nm during a d-d transition. The octahedral splitting energy for the above…EasyNumerical value

Question text from the official JEE Main paper published by NTA; answer from the final answer key. Chapter, topic and idea tags, difficulty and skill are Lumi’s. Lumi analyses 42 of the 174 JEE Main shifts held from 2017 to 2026.