Given below are two statements : Statement I : [CoBr₄]²⁻ ion will absorb light of lower energy than [CoCl₄]²⁻ ion. Statement II : In [CoI₄]²⁻ ion, the energy separation between the two set of d-orbitals is more than [CoCl₄]²⁻ ion. In the light of the above statements, choose the correct answer from the options given below :

Given below are two statements : [CoBr4]2− ion will absorb light of lower energy than [CoCl4]2− ion and energy separation in [CoI4]2− ion

Q. Given below are two statements :

Statement I : [CoBr₄]²⁻ ion will absorb light of lower energy than [CoCl₄]²⁻ ion.

Statement II : In [CoI₄]²⁻ ion, the energy separation between the two set of d-orbitals is more than [CoCl₄]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. Both Statement I and Statement II are true

C. Statement I is false but Statement II is true

D. Statement I is true but Statement II is false

Correct Answer: Statement I is true but Statement II is false

Explanation

All the given complexes, [CoCl₄]²⁻, [CoBr₄]²⁻ and [CoI₄]²⁻, are tetrahedral complexes.

In tetrahedral complexes, the crystal field splitting energy (Δ_t) depends on the nature of the ligand. According to the spectrochemical series:

Cl⁻ > Br⁻ > I⁻ (field strength decreases down the group)

Hence, the order of crystal field splitting energy is:

Δ_t([CoCl₄]²⁻) > Δ_t([CoBr₄]²⁻) > Δ_t([CoI₄]²⁻)

Statement I is true. Since [CoBr₄]²⁻ has smaller Δ_t than [CoCl₄]²⁻, it absorbs lower energy (longer wavelength) light.

Statement II is false. The iodide ligand is weaker than chloride, so the energy separation in [CoI₄]²⁻ is less, not more, than that in [CoCl₄]²⁻.

Therefore, the correct option is Statement I is true but Statement II is false.

Explanation

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