Final answer:
The conjugate acid in the equation CO3^2- + H+ ⇌ ______ ⇌ HCO3^- is HCO3^-.
Step-by-step explanation:
The conjugate acid of an acid-base reaction is formed when a base accepts a proton (H+). In the given equation, CO3^2- acts as a base by accepting a proton from H+, forming HCO3^-. Therefore, the conjugate acid in the equation is HCO3^-.