Pyrolusite is the main ore of manganese in which it is present as Its Mn content is determined by reducing it under acidic condition to `Mn^(2+)` with the help of oxalate `(C_(2)O_(4)^(2-))` ion which in turn gets oxidized to `CO_(2)` The analytical determination is carried out by adding a known excess volume of `(C_(2)O_(4)^(2-))` solution to a suspension of the pyrolusite and digesting the mixture on a hot water bath until all the `MnO_(2)` has been reduced. The excess unreacted oxalate solution is then titrated with standardized `KMnO_(4)` solution. Thereby Mn content of ore can be calculated. `KMnO_(4)`solution is also standardized under acidic condition against oxalate ion wherein `MnO_(4)^(-)` ion is reduced to `Mn^(2+)` and `(C_(2)O_(4)^(2-))` ion is oxidized to `CO_(2)`
Q An alternative method for this analysis may be the replacement of oxalate with `Fe^(2+)` But this is less frequently used because it requires some special care otherwise we get low analytical results. The probable reaction responsible for this fact is :

Options

A. presence of oxygen can cause oxidation, `Fe^(2+)toFe^(3+)`
B. presence of oxygen can cause reduction, `Fe^(3+)toFe^(2+)`
C. the oxidation of `Fe^(2+)toFe^(3+)` is difficult in the presence of `C_(2)O_(4)^(2-)`
D. formation of `CO_(2)` reduces `Fe^(3+)toFe^(2+)`

Answer

A

Explanation

Due to the pressure of oxygen, `Fe^(2+)`readily gets oxidised to `Fe^(2+)`