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Given standard electrode potentials: F...

Given standard electrode potentials:
`Fe^(3+) +3e^(-) rarr Fe, E^(@) =- 0.036` volt
`Fe^(2+) +2e^(-) rarr Fe, E^(@) =- 0.040` volt
The standard electrode potential `E^(@)` for
`Fe^(3+) +e^(-) rarr Fe^(2)` is:-

A

`-RT In X +1.29 F`

B

`-RT In X - 2.11 F`

C

`-RT In(1)/(X) +2.11F`

D

`-RT In X -1.29 F`

Text Solution

Verified by Experts

The correct Answer is:
A
Given `Au^(+3) +3e^(-) rarr E_(1)^(@) = 1.5`
`Au^(+3) +2e^(-) rarr Au^(+) rarr E_(2)^(@) = 1.4`
Ao for reaction
`Au rarr Au^(+) +e^(-) E^(@) = 2E_(2)^(@) - 3E_(1)^(@) rArr E^(@) - 1.7`
`Au +2CN^(-) rarr Au(CN)_(2)^(-) +e^(-) E^(@) = x`
`Au^(+) +e^(-) rarr E^(@) = 1.7`
`O = x +1.7 -(RT)/(F) In X - 1.7`
`x = (RT)/(F) In - 1.7`
so for reaction
`Au +2CN^(-) +(1)/(4)O_(2) +(1)/(2)H_(2)O rarr Au(CN)_(2)^(-) +OH^(-)`
`E^(@) = 0.41 +(RT)/(F) In x - 1.7 =- 1.29 +(RT)/(F) In X`
`DeltaG^(@) =- nFE^(@) (n =1)`
`DeltaG^(@) = 1.29 F - RT In x`
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