If an ore sample containing `Mn`, is treated with `50 mL` of `0.2750M Na_(2)C_(2)O_(4)` and the unreacted `Na_(2)C_(2)O_(4)` required `18.28 mL` of `0.1232 M KMnO_(4)` in acidic medium,then the number of moles of `Mn` in the ore is

Options

A. `1.38xx10^(-2)`
B. `1.49xx10^(-3)`
C. `1.15xx10^(-2)`
D. `8.12xx10^(-3)`

Answer

D

Explanation

Ore of `Mn` is `MnO_(2)` (pyrolusite)
`2e^(-)+MnO_(2)toMn^(2+)`
`(x=4)tox=+2(x=4-2=2)`
Ew of `MnO_(2)=(Mw)/(2)`
Excess of `C_(2)O_(4)^(2-)=18.28xx0.1232xx5m" Eq of "MnO_(4)^(-)`
`=11.26xx26 m" Eq of "C_(2)O_(4)^(2-)`
Total `C_(2)O_(4)^(2-)=50xx0.2750xx2 mEq=27.5mEq`
Reacted `C_(2)O_(4)^(2-)=27.5-11.26=16.24`
or `=16.24 m" Eq of "C_(2)O_(4)^(2-)`
`=16.24 m" Eq of "MnO_(2)`
`=16.24xx10^(-3) " Eq of "MnO_(2)`
Moles of `MnO_(2)=(16.24xx10^(-3))/(2)`
`=8.12xx10^(-3)mol`