A 0.13 g of a specimen containing `MnO_(2)` is treated with iodide ions. If iodine liberated requires 30.0 " mL of " 0.075 M solution of `Na_(2)S_(2)O_(3)`, the percentage of `MnO_(2)` in the mineral is

Options

A. `75.3%`
B. `85.3%`
C. `95.3%`
D. none

Answer

A

Explanation

`MnO_(2)+I^(ɵ)toI_(2)+Mn^(2+)`
`I_(2)+2Na_(2)S_(2)O_(3)toNa_(2)S_(4)O_(6)+2NaI`
`[mEq Na_(2)SO_(3)=(1xx0.075)xx30]`
`mEq Na_(2)S_(2)O_(3)=mEqI_(2)=mEq MnO_(2)`
`implies(W_(MnO_(2))/((87)/(2))xx1000=(1xx0.075)xx30`
`implies% MnO_(2)=75.3%`