Question

In a reaction :$HC{O}_3^{-}+H_{2}O\to C{O}_3^{2-}+H_3{O}^{+}$
$HC{O}_3^{-}$ is the conjugate acid of which Bronsted base ?

• A. $H_3{O}^{+}$
• B. $H_{2}C{O}_3$
• C. $C{O}_3^{2-}$
• D. None of the above

Answer 1

The correct option is C $C{O}_3^{2-}$

Carbonic acid is a polyprotic acid. It is diprotic as it has two protons. First one for the dissociation into bicarbonate ion and the second constant is for the dissociation of the bicarbonate ion into the carbonate ion.
$H_{2}C{O}_3+H_{2}O\rightleftharpoons H_3{O}^{+}+HC{O}_3^{-}HC{O}_3^{-}+H_{2}O\rightleftharpoons H_3{O}^{+}+C{O}_3^{2-}$
A Bronsted-Lowry base in an aqueous chemical reaction is one that, in the forward process, accepts a hydrogen ion in solution. We can clearly see that as the reaction proceeds, the carbonate species accepts a proton to form its conjugate acid, $HC{O}_3^{-}$.
Therefore, In this reaction, the $C{O}_3^{2-}$ species is acting as the Bronsted-Lowry base.​