Final answer:
In the titration curve for carbonate, carbonic acid (H2CO3) is the predominant species in region 1, while bicarbonate ion (HCO3-) is predominant in region 2.
Step-by-step explanation:
In the context of a titration curve for carbonate, region 1 corresponds to the initial portion where the acid-base properties of the solution are dominated by the equilibrium for dissociation of the weak acid, carbonic acid (H2CO3). Here, carbonic acid (H2CO3) is the predominant species, partially dissociating into hydrogen ions and bicarbonate ions (HCO3-).
In region 2, which is after the midpoint of the titration curve, the solution's acid-base properties are influenced by the equilibrium for reaction of the conjugate base of the weak acid with water. This refers to the bicarbonate ion (HCO3-) acting as a base and reacting with water, ultimately forming carbonate ion (CO32-) and hydronium ion. Therefore, bicarbonate ion (HCO3-) is the predominant species in this region.