Question

What is the conjugate base of ${H_2}P{O_4}^ -$?

$$A.{H_2}P{O_4} \\\ B.{H_2}P{O_4}^{2 - } \\\ C.{H_3}{O^ + } \\\ D.P{O_4}^{ - 3} \\\$$

Answer 1

We can define conjugate base as a base which is formed after an acid loses its hydrogen. Acid has a tendency to donate protons or accept an electron whereas a base has a tendency to accept protons or we can say to donate an electron.

Complete step by step answer:
Let’s start with discussing the conjugate base; conjugate base can be defined as a base which is formed after acid loses its hydrogen. So, whenever acid loses its hydrogen ion the residue that is left is termed as conjugate base as it has a tendency to accept a hydrogen atom or to be more accurate it has a tendency to donate an electron. Acid has a tendency to donate protons or accept an electron whereas a base has a tendency to accept protons or we can say to donate an electron.
Now coming to given question we have to find the conjugate base of the acid ${H_2}P{O_4}^{2 - }$
Writing its chemical equation where it loses its ${H^ + }$ ion and forms a conjugate base is
${H_2}P{O_4}^ - \to {H^ + }{\text{ }} + {\text{ }}HP{O_4}^{2 - }$
As we can see the conjugate base formed is $HP{O_4}^{2 - }$, which is formed after the acid ${H_2}P{O_4}^ -$ losses an ${H^ + }$ ion.

Hence, Option B is the correct answer.

Note:
We must know that the conjugate base and conjugate acid are two components which are formed after the respected acid and base loses their ${H^ + }$ and $O{H^ - }$ ions. They gain a tendency to obtain what they have lost, meaning in case of a conjugate base it will try to gain a proton to again become an acid and a conjugate acid will try to gain an electron to again become a base.