Following techinique is adopted to check suspected drunk drivers. Read the passage and answer the questions at the end of it. When suspected drunk drivers are tested with a Breathalyzer, the alcohol (ethanol) in the exhaled breath is oxidized to ethanoic acid with an acidic solution of potassium dichromate :
`3CH_(3)underset("Ethanol")(CH_(2)OH)(aq)+2Cr_(2)O_(7)^(2-)+16H^(+)(aq)rarr underset("Ethanoic acid")(3CH_(3)COOH)(aq)+4Cr^(3+)(aq)+11H_(2)O(l)`
The Breathalyzer measures the colour change and produces a meter reading calibrated in terms of blood alcohol content.
If the standard half-cell potential for reduction of ethanoic acid to ethanol is `0.06 V` and that of reduction of `Cr_(2)O_(7)^(2-)` to `Cr^(3+)` is `1.33 V`, then `E_("cell")^(@)` of the reaction taking place in alcohol meter is :

Options

A. `1.39 V`
B. `1.27V`
C. `-1.39 V`
D. `-1.51V`

Answer

B

Explanation

`E_("cell")^(@)=E_(Cr_(2)O_(7)^(2-)//Cl^(3+))^(@)-E_(CH_(3)OH//CH_(3)COOH)^(@)`
`=1.33-0.06=1.27V`