Question

Conjugate base for Bronsted acids ${H_2}O$and $HF$ are:

$$A.\;O{H^ - }and{\text{ }}{F^ - },{\text{ }}respectively \\\ B.\;{H_2}O{\text{ }}and{\text{ }}{F^ - },{\text{ }}respectively \\\ C.{\text{ }}{H_2}{O^ + }and{\text{ }}{F^ - },{\text{ }}respectively \\\ D.{\text{ }}{H_2}{O^ + }and{\text{ }}{H_2}{F^ + },{\text{ }}respectively \\\$$

Answer 1

Hint : We must know that the Bronsted acids are the one which donates hydrogen ion and then the acid gets converted into conjugate base.The conjugate base is able to gain or absorb a proton in a chemical reaction

Complete step by step solution :
Let’s start with understanding the concept of bronsted acid, Bronsted-lowry acid is a chemical species that donates one or more hydrogen ions in a reaction whereas the bronsted base accepts the hydrogen ion. When bronsted acid donates hydrogen ion it becomes a conjugate base. Hence, acid is the one which donates protons and base is the one which accepts it.
So, a conjugate base is being formed after the bronsted acid donates a hydrogen ion. So, for this question we are having two bronsted acids ${H_2}O$ and $HF$, the following equations will be formed when the donates one hydrogen ion each.
${H_2}O \to {\text{ }}O{H^ - }{\text{ }} + {\text{ }}{H^ + } \\\ HF{\text{ }} \to {\text{ }}{F^ - }{\text{ }} + {\text{ }}{H^ + } \\\$
So, in this the conjugate base formed are $O{H^ - }$and ${F^ - }$respectively.

So, the answer to this question is option A. $O{H^ - }$ and ${F^ - }$, respectively

Note : We must know the major difference between the bronsted and lewis acid is that in case of bronsted acid we the molecule is donating hydrogen atom and hence, converting into a conjugate base but in case of lewis acid it defines that acid is the entity which accepts the electron. So, like this both the concepts have different approaches in defining acids.