Ammonia gas dissolves in water to form $NH_4OH$. In this reaction,water acts as:

The conjugate base of $NH_4^{+}$ is

Give the classification of acids on the basis of $pK_{a}$ value.

Identify the conjugate acid-base pair respectively from the following equilibrium reaction.
$HPO_{4(aq)}^{2-} + H_2O_{(\ell)} \rightleftharpoons PO_{4(aq)}^{3-} + H_3O_{(aq)}^{+}$

When $K_2O$ is added to water,the solution becomes basic in nature because it contains a significant concentration of

What is the conjugate base of $OH^{-}$?