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Question: Which one of the following is the correct statement? (A) \(HC{O_3}^ - \,\,is\,\,conjugate\,\,base\...

Which one of the following is the correct statement?
(A) HCO3−  is  conjugate  base  of  CO32−HC{O_3}^ - \,\,is\,\,conjugate\,\,base\,\,of\,\,C{O_3}^{2 - }
(B) NH2−  is  conjugate  acid  of  NH3N{H_2}^ - \,\,is\,\,conjugate\,\,acid\,\,of\,\,N{H_3}
(C) H2SO4  is  conjugate  acid  of  HSO4−{H_2}S{O_4}\,\,is\,\,conjugate\,\,acid\,\,of\,\,HS{O_4}^ -
(D) NH3  is  conjugate  base  of  NH2−N{H_3}\,\,is\,\,conjugate\,\,base\,\,of\,\,N{H_2}^ -
(E) H2CO3  is  conjugate  base  of  HCO3−{H_2}C{O_3}\,\,is\,\,conjugate\,\,base\,\,of\,\,HC{O_3}^ -

Explanation

Solution

To solve this question, we must first understand the concepts of Conjugate acid and Conjugate base. Then we need to check for each of the given options whether they follow the property of any among conjugate acid / conjugate base and then only we can conclude the correct answer.

Complete step-by-step answer: Before we move forward with the solution of this given question, let us first understand some basic concepts:
Conjugate Acid and Conjugate Base: Conjugate acid, is a chemical compound formed when an acid donates a proton (H+)({H^ + }) to a base—in other words, it is a base with a hydrogen ion added to it, as in the reverse reaction it loses a hydrogen ion. On the other hand, a conjugate base is what is left over after an acid has donated a proton during a chemical reaction. Hence, a conjugate base is a species formed by the removal of a proton from an acid, as in the reverse reaction it is able to gain a hydrogen ion. Because some acids are capable of releasing multiple protons, the conjugate base of an acid may itself be acidic.
Step 1: Acid when it loses a proton (H+)({H^ + }) gives its conjugate base and base when accepts a proton (H+)({H^ + }) , gives its conjugate acid.
CO32−+  H+  →  HCO3−C{O_3}^{2 - } + \,\,{H^ + }\,\, \to \,\,HC{O_3}^ -
NH3  →  NH2− +  H+N{H_3}\,\, \to \,\,N{H_2}^ - \, + \,\,{H^ + } ​
HSO4−  +  H+  →  H2SO4HS{O_4}^ - \,\, + \,\,{H^ + }\,\, \to \,\,{H_2}S{O_4} ​
NH2−  +  H+→  NH3N{H_2}^ - \,\, + \,\,{H^ + } \to \,\,N{H_3} ​
HCO3−  +  H+  →  H2CO3  HC{O_3}^ - \,\, + \,\,{H^ + }\,\, \to \,\,{H_2}C{O_3}\,\,
Step 2: After going through step 1, we can clearly see that only option C is the correct statement.​

So, clearly we can conclude that the correct answer is Option (C).

Note: A cation can be a conjugate acid, and an anion can be a conjugate base, depending on which substance is involved and which acid–base theory is the viewpoint.