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Question: The conjugate base of \[H{O^ - }\] is: (A) \[{O_2}\] (B) \[{H_2}O\] (C) \[{O^ - }\] (D) \[{O...

The conjugate base of HOH{O^ - } is:
(A) O2{O_2}
(B) H2O{H_2}O
(C) O{O^ - }
(D) O2{O^{2 - }}

Explanation

Solution

The conjugate base is the negatively charged species obtained when an acid dissociates into its ionic form in the aqueous medium. HOH{O^ - } 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,
AcidH++Conjugate baseAcid \to {H^ + } + {\text{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 HOH{O^ - }.
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 HOH{O^ - } in water as:
HOH++O2H{O^ - } \to {H^ + } + {O^{2 - }}

Thus it is clear that we will obtain O2{O^{2 - }} as a negative ion when acid HOH{O^ - } will get dissociated. So, we can say from the definition of conjugate base that O2{O^{2 - }} will be the conjugate base of HOH{O^ - }.

So, the correct answer for this question is option (D) O2{O^{2 - }}.

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 HOH{O^ - } is a negatively charged species, it cannot act as an acid.