Question

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
A. `1.38 xx 10^(-2)`
B. `1.49 xx 10^(-3)`
C. `1.15 xx 10^(-2)`
D. `8.35 xx 10^(-3)`

Answer 1

Correct Answer - D
`MnO_(2) +2e^(-) Mn^(2+)` (n-factor =2)
m.eqts of unreacted `Na_(2)C_(2)O_(4) =`
`(18 xx 0.12 xx 5) =`m .eqts of `KMnO_(4) = 10.8`
Total m.equts of `Na_(2)C_(2)O_(4) = 50 xx 0.275 xx 2 = 27.5`
m.eqts of `Na_(2)C_(2)O_(4)` reacted with ore =`27.5 - 10.8 = 16.7 = 16.7 xx 10^(-3)` eqts of `MnO_(2)`
`:.` moles of `MnO_(2) = (16.7 xx 10^(-3))/(2) = 8.35 xx 10^(-3)`