In aqueous solution the ionization constants for carbonic acid are
`K_(1)=4.2xx10^(-7) and K_(2)=4.8xx10^(-11)`
Select the correct statement for a saturated 0.034 M solution of the carbonic acid.

Options

A. The concentration of `CO_(3)^(2-)` is 0.034 M
B. The concentration of `CO_(3)^(2-)` is greater than that of `HCO_(3)^(-)`
C. The concentration of `H^(+)` and `HCO_(3)^(-)` are approximately equal
D. The concentration of `H^(+)` is double that of `CO_(3)^(2-)`

Answer

C

Explanation

`H_(2)CO_(3) to H^(+) + CO_(3)^(2-) , K_(2)=4.8xx10^(-11)`
`K_(1) gtgt K_(2)`
`therefore [H^(+)]=[HCO_(3)^(-)]`
`K_(2)=([H^(+)][CO_(3)^(2-)])/([HCO_(3)^(-)])`
So, `[CO_(3)^(2-)]=K_(2)=4.8xx10^(-11)`