Solubility Rules

The solubility of ionic compounds in aqueous solutions is wide and varied. Some compounds are highly soluble (e.g. NaCl), some compounds are moderately soluble (e.g. SnI2) and some compounds are highly insoluble (e.g., AgCl). Determining which compounds are soluble and not soluble in a water medium is not a simple task. However, a set of rules that help in this regard can be stated. These rules are known as "solubility rules". Below is a set of solubility rules.

 Soluble Compounds


Almost all salts of of Na+, K+ and NH4+

All salts of Cl-, Br- and I-

 Halides of Ag+, Hg2 + and Pb2+

Compounds containing F-

Flourides of Mg 2+, Ca 2+, Sr 2+, Ba 2+, Pb 2+

Salts of nitrate, NO -3,
Chlorate, ClO3 -
perchlorate, ClO4 -
acetate, CH3CO2 -

Slats of sulfate, SO4 2-

 Sulfates of Sr 2+, Ba 2+, Pb 2+

 Insoluble Compounds


All salts of :
carbonate, CO3 2-
phosphate, PO4 3-
oxalate, C2O4 2-
chromate, CrO4 2-
sulfide, S 2-
most metal hydroxides and
oxides (OH-)

Salts of NH4 +, and the alkali metal cations

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C101 Class Notes
Prof. N. De Leon