Question

[CuCl₄]²⁻ is green. [Cu(H₂O)₆]²⁺ is blue. Which absorbs higher-energy photons? Which is predicted to have a larger crystal field splitting?

a) [CuCl₄]²⁻ absorbs higher-energy photons; Larger crystal field splitting
b) [Cu(H₂O)₆]²⁺ absorbs higher-energy photons; Larger crystal field splitting
c) [CuCl₄]²⁻ absorbs lower-energy photons; Larger crystal field splitting
d) [Cu(H₂O)₆]²⁺ absorbs lower-energy photons; Larger crystal field splitting

Answer 1

B) [Cu(H2O)6]2+ absorbs higher-energy photons and has a larger crystal field splitting compared to [CuCl4]2-.

Step-by-step explanation:

The colors of coordination complexes, such as [CuCl4]2- (green) and [Cu(H2O)6]2+ (blue), are due to the absorption of specific wavelengths of light, which is inversely proportional to the energy of the absorbed photons.

The complex with the larger crystal field splitting will absorb the higher energy (shorter wavelength) photons. Considering the given colors, a green compound absorbs light in the red portion of the spectrum (lower energy).

While a blue compound absorbs in the orange-to-red portion (higher energy). Therefore, the [Cu(H2O)6]2+ complex absorbs higher-energy photons and is predicted to have a larger crystal field splitting than [CuCl4]2-.