(I need someone to explain it using the ka values)
H2CO3 <--> HcO3- + H+ ka = 4.3x10^-7
HCO3- <--> CO3^2- + H+ ka = 5.61x10^-11
if I underestand correctly, the kb for the second equation is greater than the ka. Thus the reaction will not proceed forward, but rather produce more HCO3-. This is a basic tendency. Why is it more powerful than the first reaction?
An aqueous solution of sodium bicarbonate would be having a pH value above 7, whatever its concentration. NaHCO3 is a salt of a weak acid, H2CO3, and a strong base, NaOH. Since carbonic acid is a weak acid, it remains undissociated.