A `KMnO_(4)` solution can be standarised by titration against `As_(2)O_(3(s))`. A `0.1156 g` sample of `As_(2)O_(3)` requires `27.06mL` of the `KMnO_(4(aq.))` for its titration. What is the molarity of the `KMnO_(4(aq.))` [As `=75`]?
`5As_(2)O_(3)+4MnO_(4)^(-)+9H_(2)O+12H^(+)rarr10H_(2)AsO_(4)+4Mn^(2+)`

Explanation

Meq.of `As_(2)O_(3)=` Meq.of `KMnO_(4)`
`(As_(2)^(3+)rarr2As^(5+)rarr4e)`
`(0.1156)/(198//4)xx1000=Mxx5xx27.08`
`(Mn^(7+)+5erarrMn^(2+))`
`therefore M=0.0172`
`therefore M_(MnO_(4)^(-))=0.0172M`