Question

Amphoteric species is:
(a) $N{a_3}P{O_4} $
(b) $HS{O_4}^ - $
(c) $KOH $
(d) $HN{O_3} $
(e) ${C_2}{O_4}^{2 - } $

Answer 1

Hint: Amphoteric species are the species that have the potential to act both as an acid and as a base according to Bronsted-Lowry theory and are said to be amphoteric. The word comes from the Greek amphoteros meaning each or both of two“.

Complete answer:
Amphoteric species are a type of molecule that either accept or donate a proton $ ({H^ + }) $ , depending on the conditions. Not all the amphoteric molecules are amphiprotic. For example, $ ZnO $ acts as a Lewis acid, which can accept an electron pair from $ OH $ but cannot donate a proton.
Water, hydrogen carbonate $ (HC{O_3}^ - ) $ , dihydrogen phosphate ion $ ({H_2}P{O_4}^ - ) $ , and hydrogen sulfate ion $ (HS{O_4}^ - ) $ , are common examples of amphiprotic species. Since they can donate a proton, all amphiprotic substances contain a hydrogen atom. Also, since they can act like an acid or a base.
From the above options, the hydrogen sulfate can act as either an acid or a base in water solution, the reaction shows the acidic and basic behavior of sulfate ion with water:
 $ HS{O_4}^ - + {H_2}O \to {H_2}S{O_4} + O{H^ - } $ , sulfate ion acts as base as it accepts hydrogen ions.
 $ HS{O_4}^ - + {H_2}O \to S{O_4}^{2 - } + {H_3}{O^ + } $ , sulfate ion act as acid as it gives away hydrogen ion.
Thus, sulfate ions are an amphoteric species.
The correct option: is $ (b)HS{O_4}^ - $ .

Note:
Metal oxides or hydroxides are amphoteric. Whether a metal compound acts as an acid or base depends on the oxide oxidation state. Amphoteric molecules such as amino acids and proteins, are amphoteric. Ampholytes are amphoteric molecules that contain both acidic and basic groups and will exist mostly as zwitterions in a certain range of pH.