Question

What is acid, base, conjugate acid and conjugate base?
Identify acid, base, conjugate acid and conjugate base in the following reaction
\[N{H_3} + HCl{O_4} \to Cl{O_4}^ - + N{H_4}^ + \]
A) \[N{H_3}\]:base; \[N{H_4}^ + \]:conjugate base
B) \[HCl{O_4}\]:acid ; \[Cl{O_4}^ - \]:conjugate acid
C) \[N{H_4}^ + \]:conjugate acid; \[Cl{O_4}^ - \]:conjugate base
D) None of these

Answer 1

Hint: \[N{H_3}\] is a weak base whereas \[HCl{O_4}\] is a weak acid. We have to remember that the acid is an ion or molecule that can donate a proton \[{H^ + }\] whereas a base is a molecule or ion that can accept a proton \[{H^ + }\].
Acid can turn blue litmus red and reacts with base to form an aqueous solution whereas base turns red litmus blue and similarly reacts with acid to produce an aqueous solution.

Complete step by step answer:
Before solving this question let’s do a comparative study on acid and base.
Conjugate acid is a species that is formed when an acid donates a \[{H^ + }\]to a base or you can refer to its as a base on which a proton is attached.
Conjugate base can be referred to as the remaining part of a conjugate acid or you can say that species that accept a \[{H^ + }\].
\[N{H_3}\]: it is a weak base.
\[HCl{O_4}\]: it is a weak acid.
\[N{H_4}^ + \]: it is a conjugate acid.
\[Cl{O_4}^ - \]: it is a conjugate base.
Option A) this is an incorrect option as \[N{H_3}\] is a base which is right but its conjugate base in this reaction is \[Cl{O_4}^ - \].
Option B) This is an incorrect option as \[HCl{O_4}\] is an acid which is right but its conjugate acid in this reaction is \[N{H_4}^ + \].
Option C) this option is correct as the conjugate acid in this reaction is \[N{H_4}^ + \] whereas conjugate base is \[Cl{O_4}^ - \]
\[N{H_3} + HCl{O_4} \to Cl{O_4}^ - + N{H_4}^ + \]
Option D) this is an incorrect option as we got option C as the correct option.

Hence, the correct answer is, ‘Option C’.

Note: When an acid and a base react with each conjugate acid-base ion pair is formed. In this case both acid and base are weak. We have to remember that the acids have a pH lower than $7$ whereas a base has a pH higher than $7$.