Ionic solutions dissociate in water to form ions. For example, sodium chloride, NaCl releases Na+ and Cl- ions when dissolved in water. If another ionic solution is added to the sodium chloride solution, what happens?  It depends upon the ions present in the second solution. If the solution is silver nitrate, containing Ag+ and NO3- ions, a precipitate forms. We represent the reaction with an ionic equation:
 Na+(aq) + Cl-(aq) +  Ag+(aq) + NO3-(aq)  =  Na+(aq) + NO3-(aq) + AgCl(s)
Remember that in an ionic equation, the ions that are in a water solution have the notation (aq), from the Latin word aqua (water). The precipitate has the notation (s), for solid. Silver Chloride is relatively insoluble in water. Most of it settles out as a precipitate. This removes most of the Ag+ to form a precipitate. All other ions are called spectator ions: they are unchanged. The net result of the reaction is described by the equation:
 Ag+(aq)  +  Cl-(aq)  = AgCl(s)
On the other hand, if we add a solution of potassium nitrate to the sodium chloride solution, the results are different:
   Na+(aq) +Cl-(aq) +K+(aq) +NO3-(aq) = Na+(aq)+ NO3-(aq)+ K+(aq) +Cl-(aq)
In this case, no precipitate forms; all of the ions remain in solution. There is no net change.

How can one predict whether a precipitate will form when two solutions are mixed?  There are general guidelines, or rules, which are very useful in predicting whether a precipitate will form. In this experiment you will use the solubility rules to predict products, if any, for a series of ionic solutions.

PURPOSE:  To learn how ions react in aqueous solutions and to provide practice in writing ionic equations.

PROCEDURE:
1. Fill out the Data Table with your hypothesis as to whether a reaction will occur or not. (Hint: Use your solubility rules) If no reaction is going to occur write NR. If a reaction is going to occur write the formula for the expected precipitate.
2. Set up spot plates and perform each of the reactions. Note: Do not contaminate the solutions! Be careful not to touch the tip of a dropper to the liquid already on the plate.
3. Observe carefully to see whether a precipitate forms. It sometimes takes a few seconds for a reaction to occur. Note the color of the precipitate in the proper section of the Data Table. If no reaction forms write NR
4. When you have finished observations, write properly balanced chemical equations for all reactions that you predicted would form a precipitate. Be sure to include (aq) and (s) and charges when necessary. Note any differences between what you expected and what you actually observed.