Two electrochemical cells are assembled in which the following reactions occur `:`
`V^(2)+VO^(2+)+2H^(o+)rarr 2V^(3+)+H_(2)O`
`V^(3+)+Ag^(o+)+H_(2)O rarr VO^(2+)+2H^(o+)+Ag(s)`
Calculate `E^(c-)` for half reaction `V^(3+)+e^(-)rarr V^(2+)`
Given `: E^(c-)._((Ag^(o+)|Ag))=0.799`
`E^(c-)=E^(c-)._(V^(4+)|V^(3+))-E^(c-)._(V^(3+)|V^(2+))=0.616V`
`E^(c-)=E^(c-)._(Ag^(o+)|Ag)-E^(c-)._(V^(4+)|V_(3+))=0.439V`

Explanation

`V^(3+)+e^(-)rarr B^(2+)`
Cell Reaction `.:" " V^(2+)+VO^(2+)+2H^(o+)rarr 2V^(3+)+H_(2)O`
Half cell reaction `: V^(2+)rarrV^(3+)+e^(-)`
`V^(4+)` from` (VO^(2+))+e^(-) rarr V^(3+)`
`ulbar(V^(2+)+V^(4+)rarr V^(3+))`
`E^(c-)._(cell)=E^(c-)._(V^(4+)|V_(3+))-E^(c-)._(V^(3+)|V^(2+))`
`=0.616(` given`)" "(i)`
Second cell
`V^(3+)rarr V^(4+)+e^(-)`
`Ag^(o+)+e^(-) rarr Ag`
`ulbar(V^(3+)+Ag^(o+)rarr V^(4+)+Ag)`
`E^(c-)._(cell)=E^(c-)._(Ag^(o+)//Ag)-E^(c-)._(V^(4+)|V^(3+))`
`0.439=0.791=E^(c-)._(V^(4+)\V^(3+))`
`E^(c-)._(V^(4+)|V^(3+))=0.36V`
Substituting in `Eq. (i)`
`E^(c-)._(cell)=E^(c-)._(V^(4+)|V^(3+))-E^(c-)._(V^(3+)|V^(2+))`
`0.616=0.36-E^(c-)._(V^(3+)|V^(2+))`
`:. E^(c-)._(V^(3+)|V^(2+))=-0.256`