## Chemistry 9th Edition

$NH_4^+$ is the stronger conjugate acid.
The stronger the base, the weaker will be its conjugate acid. Judging by their $K_b$ values, methylamine is the stronger of the pair. $4.4 \times 10^{-4} \gt 1.8 \times 10^{-5}$ - $NH_4^+$ is the conjugate acid of ammonia. - $CH_3NH_3^+$ is the conjugate base of methylamine. Therefore, $CH_3NH_3^+$ is the weaker acid, and $NH_4^+$ is the stronger one.