Which of the following is the conjugate acid of HPO_3^{2-}?

• A. HPO_4^{2-}
• B. PO_3^{3-}
• C. H_2PO_3^{-}
• D. H_3PO_4

Answer: (C)

Verified step by step guidance

1. Recall that a conjugate acid is formed when a base gains a proton (H\^+).
2. Identify the given species: HPO_3^{2-} is the base in this case.
3. Add one proton (H\^+) to HPO_3^{2-} to form its conjugate acid. This increases the hydrogen count by one and decreases the negative charge by one.
4. Write the formula of the conjugate acid by adding H and adjusting the charge: HPO_3^{2-} + H\^+ \rightarrow H_2PO_3^{-}.
5. Compare the options given to confirm which matches the formula of the conjugate acid formed.