Question

Question 23 12 points) Which species is the conjugate acid of HPO42-? O A OH OB) H2PO4- OC) PO43- OD H₂O O E) P₂O

Answer 1

Conjugate acid-base pairs are differed by only one proton.

Eg. HCl(aq) + H₂O(l) $\rightarrow$ Cl^-(aq) + H₃O⁺(aq)

Here, HCl is acid and Cl^- is its conjugate base.

Also, H₂O acts as base and H₃O⁺ is its conjugate acid.

When an acid species donates a proton it becomes a conjugate base.

When a base species accepts a proton it becomes a conjugate acid.

Thus, the conjugate acid-base pairs differ only by a single proton.

Given, HPO₄^2- ion.

The conjugate acid of HPO₄^2- ion will get after it accepts a proton.

Thus, H₂PO₄^- is the conjugate acid of HPO₄^2-.

Thus, option B) H₂PO₄^- is the correct answer.