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)^(-)` ion can oxidise both `Fe^(2+)` to `Fe^(3+)` as well as `Cl^(-)` to `Cl_(2)`. So `Fe(NO_(3))_(2)` cannot be estimated quantitatively with `MnO_(4)^(-)` ion in HCl.
`E_(cell)^(@)` for the cell Pt, `Cl_(2)(g)(1atm)|Cl^(-)(aq)||MnO_(4)^(-)(aq)|Mn^(2+)(aq)`. is equal to `(1.51-1.4)=0.11V`