Answer: This is a double displacement reaction, where the cations and anions of two ionic compounds exchange places. The products of this reaction are barium phosphate and water. The driving force is the formation of a precipitate, which is an insoluble solid.
To balance the chemical equation, we need to add coefficients to make sure the number of atoms of each element is equal on both sides. The balanced equation is:
2 H 3 PO 4 ( a q) + 3 Ba(OH) 2 ( a q) → Ba 3 (PO 4 ) 2 ( s) + 6 H 2 O ( l)
To write the molecular equation, we simply use the chemical formulas of the reactants and products without separating them into ions. This is the same as the balanced equation.
To write the complete ionic equation, we separate any soluble ionic compounds or strong acids into their constituent ions. We also indicate the physical state of each substance. The complete ionic equation is:
2 H + ( a q) + 2 HPO 4 2− ( a q) + 3 Ba 2+ ( a q) + 6 OH − ( a q) → Ba 3 (PO 4 ) 2 ( s) + 6 H 2 O ( l)
To write the net ionic equation, we eliminate any spectator ions that do not participate in the reaction. Spectator ions are those that appear on both sides of the equation in identical forms. In this case, the spectator ions are H + and HPO 4 2− . The net ionic equation is:
Ba 2+ ( a q) + OH − ( a q) → Ba(OH) 2 ( s)