A particular acid-rain water has `SO_(2)` . If a 25.00 mL sample of this water requires 35 mL of 0.02 M `KMnO_(4)` for its titration, what is the molarity of `SO_(3)^(2-)` in acid-rain?
`2MnO_(4)^(-)+5SO_(3)^(2)+6H^(+)to5SO_(4)^(2-)+2Mn^(2+)+3H_(2)O`

Options

A. 0.7 M
B. 0.07 M
C. 1.07M
D. 1.7 M

Answer

B

Explanation

Meq. of `SO_(3)^(2-)` =Meq. of `KMnO_(4)`
`Nxx25=35xx0.02xx5`
N=0.14
`M=(0.14)/(2)=0.07`
`S^(4+)toS^(6+)+2e`
`M_(SO_(3)^(2-))=0.07M` (approx.)