`E^(@)` of some oxidants are given as :
`I_(2)+2e rarr 2I^(-) " " E^(@) = +0.54V`
`MnO_(4)^(-)+8H^(+)+5e rarr Mn^(2+)+4H_(2)O " " E^(@) = +1.52V`
`Fe^(3+)+e rarr Fe^(2+) " " E^(@) = +0.77V`
`Sn^(4+)+2e rarr Sn^(2+) " " E^(@) = +0.1V`
(a) Select the strongest reductant and oxidant in these.
(b) Select the weakest reductant and oxidant in these.
(c) Select the spontaneous reaction from the changes given below :
(i) `Sn^(4+)+2Fe^(2+) rarr Sn^(2+)+2Fe^(3+)`
(ii) `2Fe^(2+)+I_(2) rarr 2Fe^(3+)+2I^(-)`
(iii) `Sn^(4+)+2I^(-) rarr Sn^(2+)+I_(2)`
(iv) `Sn^(2+)+I_(2) rarr Sn^(4+)+2I^(-)`

Explanation

(a) More or `+ve` the `E_(OP)^(@)`, more is the tendency form oxidation or stronger is reductance.
Therefore, since maximum `E_(OP)^(@)`, stands for :
`Sn^(2+) rarr Sn^(4+)+2e, E_(OP)^(@) = -0.1V`
`:.` Strongest reducant :` Sn^(2+)`
and weakest oxidant : `Sn^(4+)`
(b) More or `+ve` is `E_(RP)^(@)`, more is the tendency form reduction or stronger is oxidant. Therefore, since maximum `E_(RP)^(@)` stands for : `MnO_(4)^(-)+8H^(+)+5e rarr Mn^(2+)+4H_(2)O, E_(RP)^(@) = +1.52V`
`:.` Strongest oxidant : `MnO_(4)^(-)`
and weakest reductant : `Mn^(2+)`
Note: Stronger is oxident, weaker is its conjugate reductant and vice-versa.
(c) For (i)
`E_(cell)^(@) = E_(OP_(Fe^(2+)//Fe^(3+)))^(@)+E_(RP_(Sn^(2+)//Sn^(3+)))^(@) = -0.77+0.1`
`because Fe^(2+)` oxidizes and `Sn^(4+)` reduces in change.
`E_(cell)^(@) = -0.67V`
`E_(Cell)^(@)` is negative.
`:.` (i) Is non-spontaneous change.
For (ii), `E_(Cell)^(@) = E_(OP_(Fe^(2+)//Fe^(3+)))^(@)+E_(RP_(I_(2//I^(-))))`
`= -0.770+0.54 = -0.23V`
(ii) Is non-spontaneouos change.
(iii) `E_(Cell)^(@) = E_(OP_(I^(-)//I_(2)))^(@)+E_(RP_(Sn^(4+)//Sn^(2+)))^(@)`
`= -0.54 + 0.1 = -0.44 V`
`:.` (iii) Is non-spontaneous change.
For (iv), `E_(Cell)^(@) = E_(RP_(Sn^(2+)//Sn^(4+)))^(@)+E_(RP_(I_(2)//I^(-)))`
`= -0.1+0.54 = +0.44V`