Which color is typically produced by cobalt(II) oxide (CoO) in chemical compounds or glass?

• A. Red
• B. Green
• C. Yellow
• D. Blue

Answer: (D)

Verified step by step guidance

1. Understand that transition metal oxides often impart characteristic colors to compounds or glass due to d-d electron transitions and their interaction with the crystal field.
2. Recognize that cobalt(II) oxide (CoO) is a compound of cobalt in the +2 oxidation state, which typically produces a blue color in glass or chemical compounds.
3. Recall that the blue color arises because Co(II) ions absorb certain wavelengths of light, transmitting or reflecting blue wavelengths to our eyes.
4. Note that the other colors listed (red, green, yellow) are not typically associated with CoO; for example, cobalt(II) aluminate produces a deep blue pigment known as cobalt blue.
5. Conclude that the characteristic color produced by cobalt(II) oxide in glass or compounds is blue, which is consistent with the electronic structure and common usage of Co(II) compounds.