Standard electrode potential data are useful for understanding the suitability of an oxidant in a redox titration. Some half cell reaction and their standard potentials are given below:
`MnO_(4)^(-)(aq) +8H^(+)(aq) +5e^(-) rarr Mn^(2+)(aq) +4H_(2)O(l) E^(@) = 1.51V`
`Cr_(2)O_(7)^(2-)(aq) +14H^(+) (aq) +6e^(-) rarr 2Cr^(3+)(aq) +7H_(2)O(l), E^(@) = 1.38V`
`Fe^(3+) (aq) +e^(-) rarr Fe^(2+) (aq), E^(@) = 0.77V`
`CI_(2)(g) +2e^(-) rarr 2CI^(-)(aq), E^(@) = 1.40V`
Identify the only correct statement regarding quantitative estimation of aqueous `Fe(NO_(3))_(2)`

Options

A. `MnO_(4)^(-)` can be used in aqueous HCl
B. `Cr_(2)O_(7)^(2-)` can be used in aqueous HCl
C. `MnO_(4)^(-)` can be used in aqueous `H_(2)SO_(4)`
D. `Cr_(2)O_(7)^(2-)` can be used in aqueous `H_(2)SO_(4)`

Answer

A

Explanation

`MnO_(4)^(-)` will oxidize `Cl^-` ion according to the equation,
`2MnO_(4)^(-)+16H^(+)+10Cl^(-)to2Mn^(2+)+8H_(2)O+5Cl_(2)uarr` The cell corresponding to this reaction is as follows:
`Pt,Cl_(2)("1 atm")|Cl^(-)||MnO_(4)^(-), Mn^(2+),H^(+)|Pt,`
`E_(cell)^(o)=1.51-1.40=0.11V`
`E_(cell)^(o)` bring +ve, `DeltaG^(o)` will be -ve and hence the above reaction is feasible. `MnO_(4)^(-)` will not only oxidize `Fe^(2+)` ion but also `Cl^(-)` ion simultaneously.