Question

Write the acidic equilibrium equation for HPO42

Answer 1

Explanation:

$HPO_4^{2-}$ is a conjugate base of $H_2PO_4^{-}$ but it has one acidic hydrogen which dissociates in the solution and exists in the equilibrium as shown below:

$HPO_4^{2-}+H_2O\rightleftharpoons H_3O^++PO_4^{3-}$  

The expression for the dissociation constant, $K_a$ for $HPO_4^{2-}$ is shown below as:

$K_a=\frac {[H_3O^+][PO_4^{3-}]}{[HPO_4^{2-}]}$