Question

Find the standard electrode potential of `I_(2)|2I^(c-)` if the equilibrium constant for the reaction `I_(2)+I^(c-) rarr_(3)^(c-)` is 703. The standard electrode potential of `I_(3)^(c-)|3I^(c-)` is `0.5355V`. Also give the electrode reaction.

Answer 1

`Anode:(a) 3I^(c-)rarrI_(3)^(c-)+2e^(c-)`
Cathode`(c)I_(2)+2e^(c-)2I^(c-)`
`ulbar(I_(2)+I^(c-)rarrI_(3)^(c-))`
At equilibrium `E_(cell)=0`
`E_(cell)=E^(c-)._(cell)-(0.059)/(2)log K_(eq)`
`:. E^(c-)._(cell)=(0.059)/(2)log K_(eq)`
`E^(c-).+(I_(2)|2I^(c-))-E^(c-)._(I_(3)^(c-)//3I^(c-))=(0.059)/(2) log 703`
`E^(c-)._(I_(2)|2I^(c-))--0.5355=(0.059)/(2)log 703`
`E^(c-)._(I_(2)|2I^(c-))=(0.059)/(2)log 703+0.5355`
`=(0.059)/(2)xx2.846+0.5355=0.619V`