## Chemistry: Molecular Approach (4th Edition)

(d) $CN^-$ is the strongest conjugate base.
The strength of the acid is inversely proportional to the strength of the conjugate base: The stronger the acid, the weaker its conjugate base. In order to identify the strongest conjugate base, we must find the weakest acid, which is the one with lowest $K_a$. The acid with lowest $K_a$ in this table is $HCN$; therefore, $CN^-$ is the strongest conjugate base.