Question

What will be the conjugate bases for the Bronsted acids $HF,{H_2}S{O_4}{\text{ and }}HC{O_3}^ -$ ?

Answer 1

The acidic or basic character of a substance can be determined by measuring its pH or observing the type of reactions shown by it. But in chemistry different acid-base theories are used for this classification. The concept of conjugate acid-base is given by the Bronsted -Lowry theory.

Complete answer:
The Bronsted -Lowry theory of acid-base defines an acid to be any substance capable of releasing or donating hydrogen ions into the medium and a base to be any substance capable of accepting the protons of hydrogen ions donated by the acid.
The concept of conjugate acid- base pair is based on the relationship between a Bronsted acid or base and its released counterpart. Each Bronsted acid dissociates to release hydrogen ions and an anionic remainder called the conjugate base. Similarly each Bronsted base accepts a proton and transforms into a cationic species called the conjugate acid.
Thus, the conjugate based on given Bronsted acids can be determined by segregating the hydrogen ions from the.
The reactions can be written as follows:
$HF \rightleftharpoons {H^ + } + {F^ - }({\text{conjugate base)}}$
${H_2}S{O_4} \rightleftharpoons {H^ + } + HS{O_4}^ - ({\text{conjugate base)}}$
$HC{O_3}^ - \rightleftharpoons {H^ + } + C{O_3}^{2 - }({\text{conjugate base)}}$
Thus, fluoride, hydrogen sulphate and carbonate ions are the corresponding conjugate bases of the Bronsted acids $HF,{H_2}S{O_4}{\text{ and }}HC{O_3}^ -$ respectively.

Note:
There is no compulsion for a conjugate acid or base to be an ionic species. If the Bronsted acid itself is positively charged then the species that remains after proton removal is going to be neutral and therefore a neutral conjugate base or acid is also possible.