Net Ionic Equations

Themes > Science > Chemistry > General Chemistry > Solution and Solubility > Solubility of Solutes and Aqueous Solutions > Solution Index > Net Ionic Equations

Often when working with reactions in solution, we can write a simple form of the balanced equation called a net ionic equation which eliminates ions that don't take part in the reaction. For example, the formation of solid silver chloride that occurs when you mix solutions of NaCl and AgNO₃ can be written as

Ag⁺(aq) + Cl^-(aq) -> AgCl(s)

What happened to the Na⁺ and NO₃^-? Both the salt and the silver nitrate are strong electrolytes, so they are in ion form in the solution. The sodium and nitrate ions are still in solution after the reaction- they don't change. They are known as spectator ions, and aren't important to the reaction, so we just ignore them.

Note that just like any other chemical equation, this one has the same number of atoms on both sides. (It obeys atom balance) In addition, it also has the same amount of total charge on both sides (0), so it also obeys charge balance.

Example: What is the net ionic equation when solutions of Ba(NO₃)₂ and Na₂CO₃ are mixed?

Solution: Both of the above molecules are strong electrolytes, so the solution contains Ba⁺², NO₃^-, Na⁺ and CO₃^-2 ions. Of the possible combinations of cations and anions, only BaCO₃ is insoluble: the sodium and nitrate ions do not take part in any reaction. Thus, the net ionic equation is

Ba⁺²(aq) + CO₃^-(aq) -> BaCO₃(s)

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