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Given that the standard reduction potent...

Given that the standard reduction potential `(E^(@))` of `Cr^(3+) | Cr` and `Cr^(2+) |Cr` are -0.74 and -0.91 V respectively. The `E^(@)` of `Cr^(3+) |Cr^(2+)` is:

A

`- 0.83 V`

B

`+ 0.4 V`

C

`-0.4 V`

D

`-0.18 V`

Text Solution

Verified by Experts

The correct Answer is:
C
`Cr^(3+) + 3e^(-) to Cr Delta^(@) G_(1) = - 3 xx F (-0.4)`
`Cr to Cr^(2+) + 2e^(-) Delta^(@) G_(2) = - 2 xx F xx 0.91`
`overline(Cr^(3+) + e^(-) to Cr^(2+) Delta^(@) G_(3) = Delta^(@) G_(1) + Delta^(@) G_(2)`
`Delta^(@) G_(3) = Delta^(@) G_(1) = Delta^(@) G_(2)`
`- nE_(3)^(@) F = 2.22 F + (- 1.82 F), E_(3)^(@) = - 0.4 V`
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