redox reaction, chemistry (10.8)

Question

The amount of alcohol (CH3CH2OH) in the blood can be estimated using a blower, where the exhaled ethanol is converted into acetic acid (CH3COOH) and water in the presence of oxygen gas. The magnitude of the electron current that runs from the anode to the cathode is a measure of the alcohol percentage in the blood. How many moles of electrons are transferred per mole of ethanol?

the answer is 4.

Answer 1

C₂H₅OH + O₂ → CH₃COOH + H₂O This is balanced. Since the Os in O₂ are going from the 0 to the -2 oxidation state: 4 electrons are involved in this redox reaction (You could do the half-reactions, but this is faster. You can check the Cs: 2Cs in the (+6-2)/2 = +2 state to the (4-4)/2 = 0 state. Also requiring 4 electrons)

Therefore there are 4 moles e^- /mole ethanol.