Write a structural equation to show what happens to ethanol when it is warmed with potassium dichromate.

When ethanol is heated with potassium dichromate (acidified with dilute sulfuric acid), the dichromate oxidizes the ethanol to ethanoic acid. The oxidation equation is written as:

`C_2H_5OH + H_2O -> CH_3COOH + 4H^+ + 4e^-`

Here, the ethanol gets converted to ethanoic acid. The reduction half-reaction is written as:

`Cr_2O_7^(2-) + 14H^+ + 6e^(-) -> 2Cr^(3+) + 7H_2O`

Here, dichromate ion is reduced to chromium ion. Combining the two half-reactions (oxidation and reduction), we end up with a well-balanced chemical reaction of ethanol and potassium dichromate.

`3C_2H_5OH + 2Cr_2O_7^(2-) + 16H^+ -> 3CH_3COOH + 4Cr^(3+) + 11H_2O`

This reaction takes place when an excess of potassium dichromate (oxidizing agent) is used and the ethanol is heated. If an excess of alcohol is used, we end up with an aldehyde (`CH_3CHO` ), instead of the carboxylic acid.

Hope this helps.