How many faradays of charge are required to convert:
(a). 1 mole of `MnO_(4)^(-)` to `Mn^(2+)` ion,
(b). 1 mole of `Cr_(2)O_(7)^(2-)` to `Cr^(2+)` ion

Explanation

(a). `MnO^(-)toMn^(2+), Mn^(7+)+5e^(-)toMn^(2+)`
i.e., when 1 mole of `MnO_(4)^(-)` changes to `Mn^(2+)` 5 faradays of charge is required.
(b). `Cr_(2)O_(7)^(2-)to2Cr^(3+),2Cr^(6)+.^(+)6e^(-)to2Cr^(3+`
i.e., 6 faradays of charge is required.