Which among the following species can act as an acid as well as a base according to the Brønsted-Lowry theory?

Which one is the weakest acid?

Acetic acid,$(CH_3COOH)$,has a $pK_a$ of $4.8$. Ethanol,$(CH_3CH_2OH)$,has a $pK_a$ of $16.0$. What are the major species present when acetic acid and ethanol are added to water and the $pH$ is adjusted to $7.0$?

$HF + HClO_4 \rightleftharpoons H_2F^{+} + ClO_4^-$ and $H_2O + H_2PO_4^- \rightleftharpoons H_3O^{+} + HPO_4^{2-}$ Select the group of acidic species present on the right side of the equilibrium.

Which of the following is the weakest Bronsted-Lowry base?

For the species $HSO_4^{-}$ and $NH_3$,their conjugate acids respectively are