Solubility Rules

Occurs when an ionic compound separates into its ionic components.

Not all Ionic compounds dissolve. Instead of doing experiments every time to determine solubility, we just have to follow the rules.

1. Alkali metal (Group IA) compounds are soluble.

2. Ammonium (NH4+) compounds are soluble.

3. Nitrates (NO3-), chlorates (ClO3-), and perchlorates (ClO4-) are soluble.

4. Most hydroxides (OH-) are insoluble. The exceptions are the alkali metal hydroxides and Ba(OH)2. Ca(OH)2 is slightly soluble.

5. Most chlorides (Cl-), bromides (Br-) or iodides (I-) are soluble. The exceptions are those containing Ag+, Hg+2, and Pb+2.

6. Carbonates (CO3-2), phosphates (PO4-3) and sulfides (S-2) are insoluble. The exceptions are the alkali metals and the ammonium ion.

7. Most sulfates (SO4-2) are soluble. CaSO4 and Ag2SO4 are slightly soluble. BaSO4, HgSO4 and PbSO4 are insoluble.