Final answer:
The bicarbonate ion (HCO3-) is an important ion that acts in the bicarbonate buffer system and helps maintain the acid-base balance in the blood. Though it can donate a proton and is therefore a weak acid and a weak proton donor, H2CO3 is a much stronger acid than HCO3-.
Step-by-step explanation:
The bicarbonate ion (HCO3-) is a critically important ion in body fluids where it functions in the bicarbonate buffer system. It helps to maintain the acid-base balance in the blood by buffering excess hydrogen ions (H+) and by being part of the buffer systems that absorb carbon dioxide (CO2).
The bicarbonate ion can also act as an acid in its own right, as it can donate a proton (H+) to form a carbonate ion (CO32−) through a second ionization step, although it does so in very small quantities compared to its parent acid, carbonic acid (H2CO3).
Thus, HCO3- can be identified as a bicarbonate ion, it is common in the liver where it helps regulate pH, it can be considered a weak acid, and it is indeed a proton donor, albeit a weak one compared to H2CO3.
H2CO3 is a much stronger acid than HCO3-, meaning that H2CO3 is the dominant producer of hydronium ions (H3O+) in the solution.
This is indicated by the larger ionization constant of H2CO3 compared to that of HCO3-. In simple terms, whereas H2CO3 readily dissociates in water to form H3O+ and HCO3-, the bicarbonate ion (HCO3-) only slightly dissociates to form H3O+ and CO32−.
Regarding the comparative strength of acids, the given ionization constants suggest that the equilibrium for the reaction where bicarbonate (HCO3-) acts as an acid, forming hydronium (H3O+) and carbonate (CO32−), lies far to the left, indicating it is not a strong acid.
Rather, the bicarbonate ion is better described as a weak acid and a weak proton donor in the context of Brønsted-Lowry acid-base theory.