H3PO4 + NaOH. We are asked to provide the ionic equation and net ionic equation. The ionic equation is listing all of the ions in solution in balanced form and the net ionic equation eliminates all of the unused spectator ions. Both of the reagents completely ionize in water. Since H3PO4 provides 3 protons per molecule of acid, 3 molecules of NaOH are required to fully neutralize each molecule of acid. The balanced equation is written below.
H3PO4 + 3NaOH --> 3H2O + Na3PO4
The ionic equation is written below.
3H+ + (PO4)3- + 3Na+ + 3OH- --> 3H2O + 3Na+ + (PO4)3-
The phosphate and sodium ions are spectator ions. The net ionic equation is written below.
3H+ + 3OH- --> 3H2O