Select the amphoteric substance from the following:

What is the conjugate base of $[Al(H_2O)_3(OH)_3]$?

Identify the amphoteric species among the following:
$(I) \, H_2O$
$(II) \, NH_2^-$
$(III) \, H_2PO_4^-$
$(IV) \, HCO_3^-$

What do you understand by the term 'auto-protolysis' of water? What is its significance?

The $pK_a$ of acetylsalicylic acid (aspirin) is $3.5$. If the $pH$ of human stomach fluid is $2-3$ and the $pH$ of the small intestine fluid is $8$,then aspirin will:

Identify the conjugate acid and conjugate base respectively in the following reaction:
$H_2O + HCl_{(aq)} \leftrightharpoons H_3O^{+} + Cl_{(aq)}^{-}$