Phosphoric Acid Is a Triprotic Acid, Ionizing in the Following

Multiple Choice

Phosphoric acid is a triprotic acid, ionizing in the following sequential steps: H₃PO₄  H₂O H₂PO₄^  H₃O^ H₂PO₄^  H₂O HPO₄^2  H₃O^
HPO₄^2  H₂O PO₄^3  H₃O^ Which equilibrium is most important in determining the pH of a solution of sodium phosphate?

A) HPO₄^2  H₂O PO₄^3  H₃O^
B) H₃PO₄  H₂O H₂PO₄^  H₃O^
C) PO₄^3  H₂O HPO₄^2  OH^
D) H₂PO₄^  H₂O H₃PO₄  OH^
E) 2H₂O H₃O^  OH^