Can you describe the advantages involved in expressing double displacement reactions with net ionic equations rather than with total ionic equations?
The advantage of net ionic equations is that they show only those species that are directly involved in the reaction.
Consider the reaction between silver nitrate and sodium chloride.
AgNO₃(aq) + NaCl(aq) → AgCl(s) + NaNO₃(aq)
The ionic equation is
Ag⁺(aq) + NO₃⁻(aq) + Na⁺(aq) + Cl⁻(aq) → AgCl(s) + Na⁺(aq) + NO₃⁻(aq)
The net ionic equation is
Ag⁺(aq) + Cl⁻(aq) → AgCl(s)
The net ionic equation tells us that only the Ag⁺ ions and the Cl⁻ ions are needed to form AgCl.
The Na⁺ and NO₃⁻ ions are there only to balance the charges. They do not take part in the reaction. They just watch as spectators while the Ag⁺ and Cl⁻ ions do their thing. That's why we call them spectator ions.
The net ionic equation tells us that all we need to prepare AgCl is a source of Ag⁺ ions and of Cl⁻ ions. We don't have to use just AgNO₃ and NaCl.
We can another soluble silver salt as a source of Ag⁺ ions, such as silver acetate.
We can use any soluble chloride as a source of Cl⁻ ions, such as KCl, CaCl₂, or HCl.
Any combination of these will form a white precipitate of AgCl by the same net ionic reaction.