Question

1. a. Write the net ionic equation for the predominant reaction between LiH₂PO₄and NaHSO₃(2 marks)

b.  Explain why, of the two possibilities, you decided that this would be the predominant reaction. (2 marks)

Answer 1

Ka of H2PO4- 6.23 * 10^-8 and Ka of HSO3- = 6.0 * 10^-8

So

Ka of H2PO4- and Ka of HSO3- are almost same but Ka of H3PO4 is less than that of H2SO3.

stronger acid have weak conjugate base.

Hence

H2PO4- act as base and HSO3- act as acid.

Two possibility are

1) H₂PO₄^- + HSO₃^- ......................> HPO₄^2- + H₂SO₃

2) H₂PO₄^- + HSO₃^- ......................> H₃PO₄ + SO₃^2-

Net ionic equation is

H₂PO₄^- + HSO₃^- ......................> H₃PO₄ + SO₃^2-

this would be predominant reaction.