A bettery is constructed of Cr and `Na_(2)Cr_(2)O_(7).` The unbalanced chemical equation when such a battery discharges is following:
`Na_(2) Cr_(2) O _(7)+ Cr+ H^(+)to Cr^(3+) +H_(2)O+ Na^(+)`
If one Faraday of electricity is passed through the battery during the charging, the number of moles of `Cr^(3+)` removed from the solution is

Options

A. `4/3`
B. `1/3`
C. `3/3`
D. `2/3`

Answer

C

Explanation

Reduction half reaction :
`Cr _(2) O_(7)^(2-) +6e^(-) +14H^(+) to 2Cr^(3+) +7H_(2)O`
Oxidation half reaction :
`Cr to Cr^(3+) +3e ^(-)`
Overall reaction :
`Cr_(2) O_(7)^(2-) +Cr+ 14 H^(+)+3e^(-) to 3Cr^(3+) +7H_(2)O`
3F of electricity =3 moles of `Cr ^(3+)`
If of eleclricity `=3/3` moles of `Cr ^(3+)`