The conjugate acid of PO43- is:Question 2Select one:a.PO43-b.H3PO3c.H2PO4-d.HPO42-e.H2PO42-

To determine the conjugate acid of $\text{PO}_4^{3-}$, we need to understand the concept of conjugate acids and bases. A conjugate acid is formed when a base gains a proton (H$^+$).

Steps to Identify the Correct Answer

1. Identify the Base: The given base is $\text{PO}_4^{3-}$.

2. Add a Proton: To find the conjugate acid, we add one hydrogen ion ($\text{H}^+$) to $\text{PO}_4^{3-}$.

   $\text{PO}_4^{3-} + \text{H}^+ \rightarrow \text{HPO}_4^{2-}$

3. Analyze the Options:

   • a. $\text{PO}_4^{3-}$ (not an acid)
   • b. $\text{H}_3\text{PO}_3$ (different compound)
   • c. $\text{H}_2\text{PO}_4^{-}$ (formed with one proton added)
   • d. $\text{HPO}_4^{2-}$ (correct, formed with one proton added from $\text{PO}_4^{3-}$)
   • e. $\text{H}_2\text{PO}_4^{2-}$ (not a valid species)

Final Answer

The conjugate acid of $\text{PO}_4^{3-}$ is $\text{HPO}_4^{2-}$. Thus, the correct answer is d. HPO42-.