Question

Question: Out of the following, amphiprotic species are:
(I) $HP{O_3}^{2 - }$ (II) $OH$ (III) ${H_2}P{O_4}^ - $ (IV) $HC{O_3}^ - $
A) I, III and IV
B) I and III
C) III and IV
D) All

Answer 1

Hint: Amphiprotic species: The species which can donate as well as can accept proton i.e. can act as acid as well as base, are known as amphiprotic species. For example: amino acids, water, hydrogen carbonate ions.

Complete step by step answer:
First of all we will discuss Acids, base and amphiprotic species.
1.Acids: Those species which can donate protons, are known as acids. For example: carboxylic acid.
2.Base: Those species which can accept protons, are known as base. For example: sodium hydroxide.
3.Amphiprotic species: The species which can donate as well as can accept proton i.e. can act as acid as well as base, are known as amphiprotic species. For example: amino acids, water, hydrogen carbonate ions.
4.Amino acids: These are compounds which have amine group as well as carboxylic group. Due to the presence of amine group they behave as base and due to the presence of carboxylic group they behave as acid. So they can act as both acids as well as base. Hence they are known as amphiprotic species.
In the given question we are given with the compounds (I) $HP{O_3}^{2 - }$ (II) $OH$ (III) ${H_2}P{O_4}^ - $ (IV) $HC{O_3}^ - $
Now, if we see that the compound (I) which is $HP{O_3}^{2 - }$ can act as acid but not as base. It can donate protons but cannot accept protons. Hence it is not an amphiprotic species.
The compound (II) which is $OH$ can act as base but cannot as acid. It can accept protons but cannot donate protons. Hence it is not an amphiprotic species.
The compound (III) which is ${H_2}P{O_4}^ - $ can act as base as well as acid. It can accept protons and can donate protons. Hence it is an amphiprotic species.
The compound (IV) which is $HC{O_3}^ - $ can act as base as well as acid. It can accept protons and can donate protons. Hence it is an amphiprotic species. Hence the required answer is (III) and (IV).

So, the correct answer is Option C.

Note:
When $HC{O_3}^ - $ act as acid i.e. donate proton then it forms carbonate ion and when it acts as base i.e. accept proton then it forms carbonic acid. So this is the amphiprotic species. Water is also an example of amphiprotic species because it can donate protons to form hydroxide ions and it can accept protons to form hydronium ions.