Question

In the reaction, $C{O_3}^{2 - } + {H_2}O(l) = HC{O_3}^ - + O{H^ - }(aq)$ the bicarbonate is the
A. Bronsted acid
B. Bronsted base
C. Conjugate acid
D. Conjugated base

Answer 1

According to Lowry- Bronsted theory, any species that can donate a proton or a hydrogen ion is a Bronsted acid. A base is something that can accept the proton or hydrogen ion as the Bronsted base. Conjugate acid is a compound that is formed when an acid donates a proton to a base or when a base accepts the proton. It has a hydrogen ion added to it, so we can call it a base. The conjugate base is the one with a less proton. It is the species formed after an acid donates its proton.

Complete step by step answer:
In this question, the $C{O_3}^{2 - }$ act as a base. It accepts ${H^ + }$ ions from water.
Water acts as an acid because it donates its hydrogen ions to carbonate
${H_2}O \rightleftharpoons {H^ + } + O{H^ - }$
The ${H^ + }$ ion is accepted by the carbonate $C{O_3}^{2 - }$, becoming a base.
We know that conjugate acid is a compound formed when a base accepts a proton.
Here $C{O_3}^{2 - }$ accepts ${H^ + }$ from water and forms $HC{O_3}^ -$
So we can say that $HC{O_3}^ -$ is the conjugate acid as the carbonate ion cannot be an acid in the reaction.
$O{H^ - }$ Is the conjugate base as we can see that it is formed after an acid has donated ${H^ + }$ ions

So, the correct answer is Option C.

Note: Many other theories are used to define acid and base. They are Arrhenius theory, Bronsted- Lowry theory, and Lewis theory. Arrhenius acid is that which provides ${H^ + }$ in water. Arrhenius' base is that which provides $O{H^ - }$ in water. According to Lewis's theory, acid is an electron pair acceptor and the base is an electron-pair donor.