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The standard redox potentials for the re...

The standard redox potentials for the reactions,
`MN^(2+) + 2e^(-)to Mn and Mn^(3+) + e^(-) are `-1.18V and 1.51V respectively. What is the redox potential for the reaction `Mn^(3+)+ 3e^(-) to Mn`?

A

0.33V

B

1.69V

C

`-0.28`V

D

`-0.85V`

Text Solution

Verified by Experts

The correct Answer is:
C
`Mn^(2+)+2e^(-)toMn` . . . .(i)
`DeltaG^(o)=-nFE^(o)=2.36F`
`Mn^(3+)+e^(-)toMn^(2+)` . . .(ii)
`DeltaG^(o)=-nFE^(o)=-1.51F`
Add eqns. (i) and (ii),
`Mn^(3+)+3e^(-)toMn`
`Delta^(0)=2.36F+(-1.51F)=0.85F`
`DeltaG^(0)=-nFE^(o)`
`0.85F=-3xxFxxE^(@)impliesE^(@)=-0.28V`
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