What is the color of the acidified dichromate solution before oxidation?

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

Answer: (A)

Acidified dichromate contains the Cr2O7^2− ion, which in acidic solution is orange because chromium is in the +6 oxidation state. As it oxidizes the substance, it is reduced to Cr3+, and the solution turns green. So before any oxidation occurs, the color is orange; the green color would appear after reduction, and blue or yellow don’t correspond to the chromium species present here.