## Chemistry: Molecular Approach (4th Edition)

(a) $Li^+$ is pH-neutral; (b) $CH_3N{H_3}^+$ is a weak acid; (c) $Fe^{3+}$ is a weak acid.
(a) $Li^{+}$ is the cation of a strong base $(LiOH)$, therefore, it is pH-neutral. (b) $CH_3N{H_3}^+$ is the conjugate acid of a weak base $(CH_3NH_2)$. Thus, it is a weak acid. (c) $Fe^{3+}$ is a small and highly charged metal cation. Thus, it is a weak acid.