`E^(c-)` of some elements are given as `:`
`{:(I_(2)+2e^(-)rarr 2I^(c-),,,,E^(c-)=0.54V),(MnO_(4)^(c-)+8H^(o+)+5e^(-)rarr Mn^(2+)+4H_(2)O,,,,E^(c-)=1.52V),(Fe^(3+)+e^(-)rarr Fe^(2+),,,,E^(c-)=0.77V),(Sn^(4+)+2e^(-)rarr Sn^(2+),,,,E^(c-)=0.1V):}`
`a.` Select the stronges reductant and weakes oxidant among these elements.
`b.` Select the weakest reductant and strongest oxidant among these elements.

Explanation

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