Four Co³⁺ complexes A, B, C and D contain Br⁻, NH₃, en or CN⁻ as the ligand set indicated below. The wavelengths of light they absorb are A 540 nm, B 475 nm, C 465 nm and D 310 nm. Choose the correct assignment.
Complexes: [CoBr(NH₃)₅]²⁺, [Co(NH₃)₆]³⁺, [Co(en)₃]³⁺, [Co(CN)₆]³⁻

Question

Four Co³⁺ complexes A, B, C and D contain Br⁻, NH₃, en or CN⁻ as the ligand set indicated below. The wavelengths of light they absorb are A 540 nm, B 475 nm, C 465 nm and D 310 nm. Choose the correct assignment.

Complexes: [CoBr(NH₃)₅]²⁺, [Co(NH₃)₆]³⁺, [Co(en)₃]³⁺, [Co(CN)₆]³⁻

TestHub · Accepted Answer

A stronger ligand field gives a larger Δₒ and absorption at a shorter wavelength. The spectrochemical order is Br⁻ < NH₃ < en < CN⁻, so the absorption wavelengths run 540 (Br) > 475 (NH₃) > 465 (en) > 310 (CN⁻).

Chemistry - Coordination Chemistry Question with Solution | TestHub

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