Question: In this reaction, \[N{H_4}^ + \] acts as: \[N{H_3}\left( {aq} \right) + {H_2}C{O_3}\left( {aq} \ri...

Question

In this reaction, $N{H_4}^ +$ acts as:
$N{H_3}\left( {aq} \right) + {H_2}C{O_3}\left( {aq} \right) \rightleftharpoons N{H_4}^ + \left( {aq} \right) + HC{O_3}^ - \left( {aq} \right)$

A. indicator
B. hydrate
C. acid
D. base
E. salt

Answer 1

Solution

The acid base theory gives the information about the reactants and products of a reaction. Conjugate acid and conjugate base are formed by the reaction of an acid and a base.

Complete step by step answer:
The given reaction is the reaction of an acid and base. The acid given here is the carbonic acid and the base given here is ammonia. Carbonic acid is a dibasic acid as it has two hydrogen atoms.
According to Bronstead’s acid base theory, an acid is a substance which donates protons to a base and a base is a substance which accepts protons from an acid. Acids are hydrogen ion donors and bases are hydrogen ion acceptors.
Thus the ammonia accepts protons from an acid to generate a $N{H_4}^ +$ ion. The corresponding reaction is
$N{H_3} + {H^ + } \to N{H_4}^ +$
The compound produced after accepting the proton by a base is called conjugate acid. They are collectively called a conjugate acid base pair. Thus the $N{H_4}^ +$ ion acts as a conjugate acid. Hence option C is the correct answer.
The compound produced by losing a proton from acid gives the conjugate base. Thus $HC{O_3}^ -$ is the conjugate base in this reaction.
An indicator is a substance which indicates the completion of a chemical reaction by means of color change. Thus $N{H_4}^ +$ is not an indicator.
A hydrate is a compound with composition containing some moles of water associated with the original chemical constituent. For example the copper sulphate exits in the form of copper sulfate pentahydrate.
A salt is a compound which has the composition of cations and anions present. They readily undergo dissociation in water to produce the ions.
Therefore, the correct option is C.

Note: Compounds are considered as strong Brønsted-Lowry acids if they have a strong tendency to deprotonate and the resulting conjugate base is a weak base. Also if the compound is a weak Brønsted-Lowry acid then it shows little tendency to give a proton and hence the corresponding conjugate base is a strong base.