The conjugate acid of $HPO_4^{2-}$ is

The conjugate acid of $H_2PO_4^-$ is

The $K_a$ of $CH_3COOH$ is $1.76 \times 10^{-5}$ at $298 \ K$. Calculate the dissociation constant $(K_b)$ of its conjugate base.

What is meant by the conjugate acid-base pair? Find the conjugate acid/base for the following species:
$HNO_{2}$,$CN^{-}$,$HClO_{4}$,$F^{-}$,$OH^{-}$,$CO_{3}^{2-}$,and $S^{2-}$

Which of the following cannot act both as Bronsted acid and as Bronsted base?

$A$ tribasic acid is: