Solubility 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.