What color change indicates the oxidation of K2Cr2O7?

The oxidation of potassium dichromate, K2Cr2O7, is characterized by a color change from orange to green. This change occurs because K2Cr2O7 contains chromium in the +6 oxidation state (making it orange), and upon reduction, this chromium changes to a +3 oxidation state (which is typically green).

In chemical reactions involving K2Cr2O7, such as in acidic solutions where it can act as an oxidizing agent, this distinct color transition serves as a visual indicator of the oxidation process. When K2Cr2O7 is reduced, the loss of the intense orange hue signals the formation of chromium ions that impart a green color, helping to visually confirm that a chemical change has occurred during oxidation.