If you look back at the chemical solutions you used in this experiment you will see that many of them have either nitrate as anions, or cations from Group I (sodium, potassium, etc.). Why do you think these particular compounds were used to prepare the solutions? Why not use silver chloride, for example, to prepare a solution containing silver ions?

To write chemical equations for the reactions observed, we need to recall what is happening during precipitation: ions exchange partners. At least ONE of the products is insoluble if a precipitate forms. Molecular reactions show the simple ion trade but not ions themselves.

These molecular reactions give the basic information about the processes such as the ratios in which the substances react, but they don't represent accurately what is happening. Since all of these compounds are electrolytes in solution, they actually exist as separated ions, not ion pairs like NaCl. And if only one of the "products" is insoluble, the other actually never forms.