What `%` of the carbon in the `H_(2)CO_(3)-HCO_(3)^(-)` buffer should be in the form of `HCO_(3)^(-)` so as to have a neutral solution? `(K_(a)=4xx10^(-7))`

Options

A. `20%`
B. `40%`
C. `60%`
D. `80%`

Answer

D

Explanation

`pH=pK_(a)+log``([HCO_(3)^(-)])/([H_(2)CO_(3)])`
`implies 7=7-log4+log``([HCO_(3)^(-)])/([H_(2)CO_(3)])implies ([HCO_(3)^(-)])/([H_(2)CO_(3)])=4`
`%` of carbon in the form of `HCO_(3)^(-)`
`=([HCO_(3)^(-)])/([HCO_(3)^(-)]+[H_(2)CO_(3)])xx100=(4)/(1+4)xx100=80%`