Final answer:
The conjugate acid of HPO3²− is obtained by adding a proton, resulting in H2PO3, which is option A: H2PO3.
Step-by-step explanation:
The conjugate acid of a base is formed by adding a proton (H+) to that base. In chemical terms, a base is a substance that can accept protons, and when it does so, it becomes an acid. The ions or molecules become conjugate acids which have one more hydrogen ion (H+) than the original base.
The ion we are looking at is HPO32−, and to find its conjugate acid, we need to add a hydrogen ion (H+) to it. When we add a proton to HPO32−, we get H2PO3−, which is option A: H2PO3. This is because HPO32− gains a proton thus decreasing its negative charge by one.
If we were to add another proton, we would get H3PO3, which is not among the given options, and adding further two protons would yield H3PO4, which is not the next logical step from our given base, nor is it one of the listed options. Therefore, the correct option that represents the conjugate acid of HPO32− is option A, H2PO3.