Question

which of the following reasons correctly explains the color changes that take place when 8 ml of the 10% h2o2 is added to the solution of dichlorobis(ethylenediamine)cobalt(ii)? the ethylenediamine ligands surrounding the cobalt metal center are being replaced by peroxide ligands which results in a different crystal field splitting. thus, the energy associated with electron transitions between the d-orbitals will differ for the two compounds showing a color change. the ethylenediamine ligands are oxidized which results in a different crystal field splitting. thus, the energy associated with electron transitions between the d-orbitals will differ for the two compounds showing a color change. the cobalt(ii) metal ion center is oxidized to a cobalt(iii) metal ion center which results in a different crystal field splitting. thus, the energy associated with electron transitions between the d-orbitals will differ for the two compounds showing a color change. the cobalt(ii) metal ion center is reduced to a cobalt(i) metal ion center which results in a different crystal field splitting. thus, the energy associated with electron transitions between the d-orbitals will differ for the two compounds showing a color change.

Answer 1

The color change upon adding H2O2 to a cobalt(II) complex occurs because the cobalt ion is oxidized to cobalt(III), altering the crystal field splitting and shifting the d-d electron transitions.

Step-by-step explanation:

The student's question concerns the reason behind the color change observed when a solution of dichlorobis(ethylenediamine)cobalt(II) reacts with hydrogen peroxide (H2O2). The correct explanation is that the hydrogen peroxide acts as an oxidizing agent, converting the cobalt(II) metal ion center to a cobalt(III) metal ion center. This process alters the crystal field splitting around the cobalt ion, leading to a change in the energy levels of the d-orbitals. Consequently, the d-d electron transitions that cause the compound to absorb and reflect certain wavelengths of light change, which is observed as a change in color of the solution.

Transition metal compounds, including those of cobalt, are often colored due to d-d transitions, where electrons in the d-orbitals absorb photons and jump to higher energy levels. The energy differences between these orbitals—affected by the oxidation state of the metal and the field strength of the ligands—determine the color of light absorbed. After the addition of H2O2, which is a strong oxidizer, the cobalt ion is oxidized, and the electronic structure changes significantly. This phenomenon is similar to color changes observed in aqueous metal ions with different ligands or oxidation states, as indicated in Figure 19.38, and the vanadium complexes.

Answer 2

The ethylenediamine ligands surrounding the cobalt metal center are being replaced by peroxide ligands, which results in a different crystal field splitting and a color change.

Step-by-step explanation:

The correct reason for the color changes is that the ethylenediamine ligands surrounding the cobalt metal center are being replaced by peroxide ligands, which results in a different crystal field splitting. This leads to a difference in the energy associated with electron transitions between the d-orbitals, causing a color change.