Final answer:
To determine if a compound forms ions in an aqueous solution, use the solubility rules, which dictate if a compound is soluble or forms a precipitate. Compounds that are soluble dissociate into ions, whereas insoluble compounds form a solid precipitate.
Step-by-step explanation:
To determine if a compound can form ions when dissolved in an aqueous solution, you must consider the solubility rules. These rules help us predict whether a compound will remain as ions in solution or form a precipitate (an insoluble solid). For instance, most compounds of the alkali metals (Li+, Na+, K+, etc.) and the ammonium ion (NH4+) are soluble in water and therefore will typically dissociate into ions when dissolved. Similarly, nitrates (NO3-) and acetates (C2H3O2-) are also generally soluble. By following the solubility rules, if the rules state a compound is soluble, it is labelled (aq) to indicate that it dissolves and remains as ions in the aqueous solution. If, however, the rules indicate that the compound is insoluble, it forms a solid precipitate, labeled (s), and does not dissociate into ions.
Using equilibrium constant expressions can further quantify the concentration of ions in equilibrium with the solid in solution. In the case of dissolution by complex ion formation, such as when aqueous ammonia is added to a mixture of silver chloride and water, the silver chloride dissolves slightly, releasing Ag+ ions into the solution.