The conjugate base of $H_{2}PO_{4}^{-}$ is:

The compound that is not a Lewis acid is

In the following reaction:
$[Al(H_2O)_6]^{+3} + HCO_3^{-} \rightleftarrows [Al(H_2O)_5OH]^{+2} + H_2CO_3$
$(A)\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad(B)\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad(C)\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad(D)$
Which species behave as Bronsted-Lowry acids?

The conjugate base of $H_2PO_4^-$ is

$BF_3$ acts as an acid according to .............

What is a Lewis acid?