In this example problem, we write the balanced molecular, complete ionic, and net ionic equations for a precipitation reaction. Our problem reads, "Write the balanced molecular, complete ionic, and net ionic equations for the reaction between aqueous calcium acetate and aqueous sodium carbonate." Let's start by writing the balanced molecular equation. Calcium acetate reacts with sodium carbonate in a precipitation reaction, whereby we have two soluble ionic compounds reacting to produce an insoluble ionic compound called the precipitate, which is determined according to our solubility rules. When we switch cations and anions for the reactants, we produce sodium acetate and calcium carbonate. According to our solubility rules, sodium acetate is soluble but calcium carbonate is insoluble, so sodium acetate is written as aqueous (aq) and calcium carbonate is written as solid (s). Now we need to balance it. Since we have all ionic compounds and our ions don't change from reactants to products, we can balance ions instead of atoms. This has the benefit of keeping polyatomic ions together as we're balancing. We want to balance calcium ions, acetate ions, sodium ions, and carbonate ions. Since all of our ions show up in only one place on each side, we can balance them in any order. Let's start with calcium ions. Right now, we have 1 calcium on the left and 1 calcium ion on the right with coefficients of 1 before calcium acetate and calcium carbonate. We have two acetate on the left and we can get two on the right by adding a two coefficient before sodium acetate. Now we have two sodium on the right and we can get two sodium on the left with a one coefficient before sodium carbonate. And we have one carbonate on both sides. When we write our balanced chemical equation, we do not write out the implicit 1 coefficients. When we write out the complete ionic equation, we separate any strong electrolytes into their compound ions. Strong electrolytes are strong acids and soluble ionic compounds. We know whether or not an ionic compound is soluble based on its solubility rules. Our soluble ionic compounds are calcium acetate, sodium carbonate, and sodium acetate in this equation. Calcium carbonate is an insoluble ionic compound, so it does not break apart into ions in solution. It comes out of solution as a solid. We cannot break it apart in the complete ionic equation. When we break apart soluble ionic compounds for the complete ionic equation, we multiply the coefficient times the number of ions in the formula unit. There is one calcium acetate, and each calcium acetate has one calcium ion, so we have one calcium ion in the complete ionic equation. There's one calcium acetate, and each calcium acetate has two acetate ions, so we have two acetate ions in the complete ionic equation. Likewise, one sodium carbonate times two sodium ions in each sodium carbonate is two sodium ions. One sodium carbonate times one carbonate ion means we have just one carbonate ion in our complete ionic equation. Two sodium acetate times one sodium ion per sodium acetate means we have two sodium ions. And two sodium acetate times one acetate ion in each sodium acetate means we have two acetate ions. Calcium carbonate is a solid, so we cannot break it apart. It's not a strong electrolyte. This is our complete ionic equation. To create the net ionic equation, we need to remove spectator ions, which show up exactly the same on both sides of the equation. We have two acetate ions on both sides and two sodium ions on both sides, so we can remove both of these to form the net ionic equation. What's left over is one calcium ion plus one carbonate ion produces solid calcium carbonate. This is our net ionic equation.