There are many other factors that can affect solubility, but these rules are a good first step to determine the outcome of aqueous solution reactions. When equilibrium is reached, the solution is saturated, and that concentration defines the solubility of the solute. Ca(OH) 2 is slightly soluble. These rules provide guidelines that tell which ions form solids and which remain in their ionic form in aqueous solution. 2. Predicting Precipitates Using Solubility Rules. 1. Solubility Rules Whether or not a reaction forms a precipitate is dictated by the solubility rules. Alkali metal (Group IA) compounds are soluble. Substances with relatively low solubilities are said to be insoluble, and these are the substances that readily precipitate from solution. Nitrates (NO 3-), chlorates (ClO 3-), and perchlorates (ClO 4-) are soluble. Depending on the solubility of a solute, there are three possible results: 1) if the solution has less solute than the maximum amount that it is able to dissolve (its solubility), it is a dilute solution; 2) if the amount of solute is exactly the same amount as its solubility, it is saturated; 3) if there is more solute than is able to be dissolved, the excess solute separates from the solution. If solutions of sodium nitrate and ammonium chloride are mixed, no reaction occurs. Solubility changes with temperature, so if you look up solubility data it will specify the temperature. Ammonium (NH 4 +) compounds are soluble. 4. Solubility Rules Whether or not a reaction forms a precipitate is dictated by the solubility rules. However, some combinations will not produce such a product. A substance will precipitate when solution conditions are such that its concentration exceeds its solubility. The Solubility Rules. Substances with relatively large solubilities are said to be soluble. 3. 2 KCl (aq) + Pb (NO 3) 2 (aq) → 2 KNO 3 (aq) + PbCl 2 (s) The solubility rules are a useful guideline to predict whether a compound will dissolve or form a precipitate. Most hydroxides (OH-) are insoluble. One could write a molecular equation showing a double-replacement reaction, but both products, sodium chloride and ammonium nitrate… 5. Solubility Rules as a List The solubility of ionic compounds in water at 25°C, in general: All compounds of the ammonium ion (NH 4+) are soluble. The exceptions are the alkali metal hydroxides and Ba(OH) 2. Solubility is the maximum possible concentration, and it is given in M, g/L, or other units. Some combinations of aqueous reactants result in the formation of a solid precipitate as a product. If this separation … These rules provide guidelines that tell which ions form solids and which remain in their ionic form in aqueous solution. Use the solubility rules (list, table or chart) to decide if either of the ionic compounds are insoluble and will therefore form a precipitate.