Question

Out of the following, amphiprotic species are:
(I) $HPO_3^{ - 2}$ (II) OH (III) ${H_2}PO_4^ - $ (IV) $HCO_3^ - $
A. I, III, IV
B. I and III
C. III and IV
D. All

Answer 1

Hint: Amphiprotic species behaves as acid as well as base. The species contains both properties, it acts as an amphiprotic species. It must be able to accept hydronium ion or give away also hydronium ion. Amphiprotic species accept a proton or donate away its proton. This can help to determine the difference between amphiprotic and amphoteric.

Complete step by step answer:
Amphiprotic species remove hydrogen ions from an acid or by adding hydrogen ions to a base. It acts as acid as well as base. They contain properties of acid or base.
Amphiprotic species either donate protons or accept protons which depend on their circumstances.
Here, ${H_2}PO_4^ - $ and $HCO_3^ - $ both are amphiprotic species. Both species act as acid as well as base.
Their structure is shown below:

As we see the structure of species which act as acid or base. Both structures are an amphiprotic species.
The bicarbonate act as acid or base in water, which is defined by the following reactions:
 \[
  HCO_3^ - + {H_2}O \to CO_3^{ - 2} + {H_3}{O^ + } \\
  HCO_2^ - + {H_2}O \to {H_2}C{O_3} + O{H^ - } \\
 \]
As it is ${H_2}PO_4^ - $ also acts as acid as well as base.

Hence option (C) is the correct.

Note:
Amphiprotic substances can accept or donate at least one proton. So, in order for a substance to be amphiprotic, it must be able to accept proton ions or give away proton ions. These species behave like an acid in basic media and behave like base when present in an acidic medium.