Protolysis reaction

Question

Hi, have I done the following question correctly?

Write a protolytic reaction where HPO₄^2- is shown as a

a) acid

b) base

a) I look at the table of base constants and chose a base with higher base constant than HPO42- to react with it, like CO32-

So reaction: HPO₄^2- + CO₃^2- <-> PO₄^3- + HCO₃^-

b) This time I chose a base with lower base constant, so that the HPO42- can act as a base instead, so I chose HSO3- to react with it.

So reaction HPO₄^2- + HSO₃^- <-> H₂PO₄^- + SO₃^2-

Are my thoughts and answers correct?

Answer 1

Yes. You did both correctly. I'm guessing, however, that the question may only require a generic format rather than having to use a table of Ka and Kb (or pKa and pKb). So, maybe you could have just answered the question generically as...

a) HPO₄^2- + B ==> BH⁺ + PO₄^3- where B is a base

b) HPO₄^2- + HA ==> H₂PO₄^- + A^- where HA is an acid