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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^(-) |
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Answer» Solution :(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` `becauseFe^(2+)` oxidizes and `Sn^(4+)` reduces in change. `E_(cell)^(@) = -0.67V` `E_(Cell)^(@)` isnegative. `:.` (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` |
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