Question
Question: The conjugate base of \[H{O^ - }\] is: (A) \[{O_2}\] (B) \[{H_2}O\] (C) \[{O^ - }\] (D) \[{O...
The conjugate base of HO− is:
(A) O2
(B) H2O
(C) O−
(D) O2−
Solution
The conjugate base is the negatively charged species obtained when an acid dissociates into its ionic form in the aqueous medium. HO− can act as an acid as it has a removable proton.
Complete step by step answer:
We know that Bronsted-Lowry theory includes the concept of conjugate acids and conjugate bases.
Let’s know what characterizes the conjugate base.
- We know according to Bronsted-Lowry theory that when acid dissolves in aqueous medium, it gets dissociated into proton and a negatively charged ion. This negatively charged ion is termed as a conjugate base of this acid. So, we can write that,
Acid→H++Conjugate base
As an example, we can write that when hydrochloric acid dissolves in aqueous media, it dissociates into a proton and chlorine ion, so here chlorine ion is the conjugate base of hydrochloric acid.
Now, we are asked what will be the conjugate base of HO−.
Look, whenever we are being asked to find a conjugate base of some species, then we should accept that a given species would act as an acid and will give a proton when it gets dissociated into aqueous media. So, we can write that dissociation reaction of HO− in water as:
HO−→H++O2−
Thus it is clear that we will obtain O2− as a negative ion when acid HO− will get dissociated. So, we can say from the definition of conjugate base that O2− will be the conjugate base of HO−.
So, the correct answer for this question is option (D) O2−.
Note:
Do not get confused between conjugate acid and conjugate base. Conjugate acid is a species which is formed when a base accepts a proton. Do not think that as HO− is a negatively charged species, it cannot act as an acid.