JEE Main 2026 — Jan 23, Shift 1 — Chemistry solution

JEE Main2026Jan 23, Shift 1Chemistry

Given below are two statements :

Statement I : [CoBr $_{4}$ ] $^{2 -}$ ion will absorb light of lower energy than [CoCl $_{4}$ ] $^{2 -}$ ion.

Statement II : In [CoI $_{4}$ ] $^{2 -}$ ion, the energy separation between the two set of d-orbitals is more than [CoCl $_{4}$ ] $^{2 -}$ ion.

In the light of the above statements, choose the correct answer from the options given below :

A
Both Statement I and Statement II are false
B
Statement I is true but Statement II is false
C
Statement I is false but Statement II is true
D
Both Statement I and Statement II are true

Solution

The spectrochemical series gives ligand field strength: I $^{-}$ $<$ Br $^{-}$ $<$ Cl $^{-}$ .

Statement I: Weaker-field Br $^{-}$ gives a smaller $Δ_{t}$ than Cl $^{-}$ , so [CoBr $_{4}$ ] $^{2 -}$ absorbs photons of lower energy (longer wavelength). True.

Statement II: I $^{-}$ is even weaker than Cl $^{-}$ , so [CoI $_{4}$ ] $^{2 -}$ has a smaller d-orbital splitting than [CoCl $_{4}$ ] $^{2 -}$ , not larger. False.

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