A certain monobasic acid is found to be soluble in a aqueous sodium carbonate but insoluble in aqueous sodium bicarbonate . If the ionization constant for carbonic acid are 3x10-7 and 6x10-11. The ionization constant for the acid must be:

Question

aaronq · Answer

carbonic acid, H2CO3

1st dissociation:    H2CO3 ->HCO3- + H+;  Ka1=3x10^-7
2nd dissociation:   HCO3- -> CO3^2-   + H+; Ka2=6x10^-11

HA soluble in sodium carbonate Na2CO3 (it can protonate CO3^2-)

HA insoluble in sodium bicarbonate NaHCO3 (it can't protonate HCO3-)

so, i think the ionization constant should be more than Ka2 but less than Ka1.