Write the conjugate base for each of the following:
a. HPO4^-2 ____________________
b. H2O ____________________
To find the conjugate base for an acid, you need to remove a proton (H+) from the acid molecule.
a. HPO4^-2 is the conjugate base of its respective acid, which is H2PO4^-1. To find the conjugate base, remove one H+ from the acid, so the answer is PO4^-3.
b. H2O is a neutral molecule without an excess proton (H+) to remove, so it does not have a conjugate base.