Observe the following species: $AlCl_3, NH_3, H^{+}, Co^{3+}, OH^{-}, Mg^{2+}, BF_3, Cl^{-}$. How many Lewis acids are present in the above list?

What will be the conjugate bases for the following Bronsted acids: $HF$,$H_{2}SO_{4}$ and $HCO_{3}^{-}$?

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?

Which statement about the following equilibrium is true?
$(CH_3)_3CO^-K^+ + H_2O \rightleftharpoons (CH_3)_3COH + K^+OH^-$
Given: $pK_a(H_2O) = 15.7$,$pK_a((CH_3)_3COH) = 18$

The conjugate acid of $H_2PO_4^-$ is

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