To neutralize completely `20 mL` of `0.1M` aqueous solution of phosphorus `(H_(3)PO_(3))` acid the volume of `0.1M` aqueous `KOH` solution required is:

Options

A. `10mL`
B. `20mL`
C. `40mL`
D. `60mL`

Answer

C

Explanation

`H_(3)PO_(3)` is a dibasic acid (i.e. contains two ionisable protons attached directly to O).
`H_(3)PO_(3)hArr2H^(+)+HPO_(3)^(2-)`
`:.0.1MH_(3)PO_(3)=0.2NH_(3)PO_(3)`
`" and "0.1M"KOH"=0.1N"KOH"`
`underset((KOH))(N_(1)V_(1))=underset((H_(3)PO_(3)))(N_(2)V_(2))`
`0.1V_(1)=0.2xx20`
`rArrV_(1)=40mL`