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E^(c-) for Cr^(3+)+3e^(-) rarr Cr and Cr...

`E^(c-)` for `Cr^(3+)+3e^(-) rarr Cr `and `Cr^(3+)+e^(-) rarr Cr^(2+)` are `-0.74 V` and `-0.40V`, respectively, `E^(c-)` for the reaction is `Cr^(+2)+2e^(-) rarr Cr`

A

`-0.91V`

B

`+0.91V`

C

`-1.14V`

D

`+0.34V`

Text Solution

Verified by Experts

The correct Answer is:
a
`Cr^(3+)+3e^(-) rarr Cr,`
`Cr^(3+)+e^(-) rarr Cr^(2+), `
`ulbar(Cr^(2+)+2e^(-) rarr Cr,)`
`E^(c-)._(3)=(n_(1)E^(c-)._(1)-nE^(c-)._(2))/(n_(3))`
`=([3xx(-0.74)]-[(-1)xx(-0.40)])/(2)=-0.91V`
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