Final answer:
b. conjugate base.In the reaction HCO3- + H2O -> H3O+ + CO32-, H2O acts as the acid and its conjugate base after donating a proton is OH-.
Step-by-step explanation:
In the forward chemical equation: HCO3−+H2O → H3O+ + CO32−, we can identify the acid, base, conjugate acid, and conjugate base. Water (H2O) is acting as the acid in this reaction because it donates a proton (H+) to the bicarbonate ion (HCO3−).
Upon donating a proton, water becomes its conjugate base, which is the hydroxide ion (OH−). Conversely, the bicarbonate ion (HCO3−), which is accepting a proton, is the base and it becomes its conjugate acid upon gaining a proton to form carbonic acid (H2CO3),
which is not shown but implied as H3O+ and CO32− are the products of such dissociation.