## Chemistry: The Central Science (13th Edition)

$HP{O_4}^{2-}$ is the stronger base.
The weaker the acid, the stronger its conjugate base. Therefore, if we determine which conjugate acid is weaker, we will get the stronger base: Conjugate acids: $H_2P{O_4}^-$ and $H_3PO_4$; Since it is easier to take a proton from a neutral compound, $H_3PO_4$ is the stronger acid, and $H_2P{O_4}^-$ is the weaker, which makes $HP{O_4}^{2-}$ the stronger base.