Chapter 19, Problem 19.101SP

When suspected drunk drivers are tested with a Breathalyzer the alchol (ethanol) in the exhaled breath is oxidized to acetic acid with an acidic solution of potassium dichromate:

$3C{H}_{3}C{H}_{2}OH(aq)+2CrO{7}^{2-}(aq)+16H^{+}(aq)\to 3C{H}_{3}C{O}_{2}H(aq)+4C{r}^{3+}(aq)+11H_{2}O(l)$
The color of the solution changes because same of the orange $C{r}_2{O}_7{}^{2-}$ is converted to the green $C{r}^{3+}$ The Breathalyzer measures the color change and produces a meter reading calibrated in blood alcohol content.
(a) What is P for the reaction if the standard half-cell potential for the reduction of acetic acid to ethanol is 0.05 8 V?
(b) What is the value of E for the reaction when the concentrations of ethanol, acetic acid, $C{r}_2{O}_7{}^{2-}$ , and $C{r}^{3+}$ are 1.0 M and the pH is 4.00?