When suspected drunk drivers are tested with a Breathalyzer,the alcohol (ethanol) in the exhaled breath is oxidized to acetic acid with an acidic solution of potassium dichromate: 3CH₃CH₂OH(aq) + 2Cr₂O₇^-2 (aq) + 16H⁺(aq) 3CH₃CO₂H(aq) + 4Cr⁺³(aq) + 11H₂O (l)
If Eº for this cell is 1.30V and the standard half-cell potential of Cr₂O₇^-2(aq) to Cr⁺³ is 1.358 V,what is the standard half-cell reduction potential for the conversion of acetic acid to ethanol?

Question

Quizplus · Accepted Answer

The oxidation reaction of ethanol to acetic acid can be written as: 
CH3CH2OH + 2[O] → CH3COOH + H2O
The reduction half-reaction can be obtained by reversing the oxidation half-reaction and changing the sign of the cell potential:
CH3COOH + H2O + 2e- → CH3CH2OH + 2OH-
The standard reduction potential for this reaction can be calculated using the Nernst equation:
Eºcell = Eºreduction - Eºoxidation
1.30 V = Eºreduction - 1.358 V
Eºreduction = -0.058 V (Option D)

When Suspected Drunk Drivers Are Tested with a Breathalyzer,the Alcohol