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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

`0.33 V`

B

`1.69 V `

C

`-0.28 V `

D

`-0.85 V`

Text Solution

Verified by Experts

The correct Answer is:
C
`Mn^(2+) + 2e^(-) to Mn`
`Delta G^(@) = - nFE^(@) = 2.36 F " " …. (i)`
`Mn^(3+) + e^(-) to Mn^(2+)`
`Delta G^(@) = - n FE^(@) = -1.51 F " " …. (ii)`
Adding eq. (i) and (ii)
`Mn^(3+) + 3e^(-) to Mn`
`Delta G^(@) = 2.36 F + (-1.51 F) = 0.8 5 F`
`Delta G^(@) = - n FE^(@)`
`0.85 F = -3 xx F xx E^(@)`
or `E^(@) = - (0.85)/(3) = -0.28 V `
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MODERN PUBLICATION-ELECTROCHEMISTRY -COMPETITION FILE (OBJECTIVE TYPE QUESTIONS) B MULTIPLE CHOICE QUESTIONS
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