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Breathalyzer is used to detect the alcoh...

Breathalyzer is used to detect the alcohol content in the suspected drunk drivers. The ethanol in the exhaled breath is oxidized to ethanoic acid with an acidic solution of `K_(2)Cr_(2)O_(7)` as follows `:`
`underset(Ehanol)(3CH_(3)CH_(2)OH(aq))+2Cr_(2)O_(7)^(2-)(aq) +16H^(o+)(aq) rarr underset(Ethanoic ac i d)(3CH_(3)COH(aq))+4Cr^(3+)(aq)+11H_(2)O(l)`
The breathalyzer measures the colour change and produces a metre reading calibrated in the terms of blood alcohol content.
If `E^(c-)._(CH_(3)COOH|C_(2)H_(5)OH)=0.06 V` and `E^(c-)._(Cr_(2)O_(7)^(2-)|Cr^(3+))=1.33V`,
then `E^(c-)._(cell)` of the reaction taking place in alcohol metre is

A

`1.39V`

B

`1.27V`

C

`-1.39 V`

D

`-1.51V`

Text Solution

Verified by Experts

The correct Answer is:
b
`E^(c-)._(cell)=(E^(c-)._(Cr_(2)O_(2)^(2-)|Cr^(3+)))_(reduction at cathode )-(E^(c-)._(CH_(3)COOH|C_(2)H_(5)OH))_(reduction at anode )`
`=1.33-0.06=1.27V`
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