We’re asked to determine the approximate relative quantities of each of the three species involved in the reaction.
The three species involved and their given pKa values are:
H2CO3 ⇄ HCO3- ⇄ CO32-
pKa: 6.35 10.33
The dissociation will happen if the pH value overcomes the pKa value for the specific species.
H2CO3 is a diprotic acid. The pKa for H2CO3 is 6.35, and the pKa for HCO3- is 10.33. At pH = 7.2 what is the "approximate" relative quantities of H2CO3, HCO- and CO32-?