A particular acid-rain water has `SO_(3)^(2-)`. If a `25.00 mL` sample of this water requires `34.08 mL` of `0.01964M KMnO_(4)` for its titration, what is the molarity of `SO_(3)^(2-)` in acid-rain?
`2MnO_(4)^(-)+5SO_(3)^(2-)+6H^(+)rarr5SO_(4)^(2)+2Mn^(2+)+3H_(2)O`

Explanation

Meq.of. `SO_(3)^(2-)="Meq.of" KMnO_(4)`
`therefore Nxx25=34.08xx0.01964xx5`
`N=0.1339`
`therefore M=(0.1339)/(2)=0.0669`
`S^(4+)rarrS^(6+)+2e`
`N_(SO_(3)^(2-))=0.1339N`
`M_(SO_(3)^(2-))=(0.1339)/(2)=0.0669M`