Rules for Learning the Solubility of Ionic Compounds in Water

 

Negative Ions
(Anions) 		+ Positive Ions
(Cations) 		= Solubility of compounds in water Example
any anion + alkali ions
(Li+,Na+,K+,Rb+,Cs+,Fr+) 		= soluble sodium fluoride, NaF, is soluble
any anion + hydrogen ion
[H+(aq)] 		= soluble sodium hydride, NaH, is soluble
any anion + amonium ion
(NH4+) 		= soluble ammonium chloride, NH4Cl, is soluble
nitrate
NO3- 		+ any cation = soluble potassium nitrate, KNO3, is soluble
acetate
(CH3COO-) 		+ any cation = soluble sodium acetate, CH3COONa, is soluble
Chloride (Cl-), Bromide (Br-), Iodide (I-) + silver (Ag+), lead (Pb2+), mercury (Hg2+), copper (Cu+), thallium (Tl+) = low solubility (insoluble) silver chloride, AgCl, forms a white precipitate (a white solid)
+ any other cation = soluble potassium bromide, KBr, is soluble
Suphate
(SO42-) 		+ calcium (Ca2+), strontium (Sr2+), barium (Ba2+), silver (Ag+), lead (Pb2+), radium (Ra2+) = low solubility (insoluble) barium sulphate, BaSO4, forms a white precipitate (a white solid)
+ any other cation = soluble copper sulphate, CuSO4, is soluble
Sulfide
S2- 		+ alkali ions (Li+,Na+,K+,Rb+,Cs+,Fr+), alkali earth metals (Be2+,Mg2+,Ca2+,Sr2+,Ba2+,Ra2+),
and H+(aq), NH4+ 		= soluble magnesium sulfide, MgS, is soluble
+ any other cation = low solubility (insoluble) zinc sulfide, ZnS, is insoluble
Hydroxide
OH- 		+ alkali ions (Li+,Na+,K+,Rb+,Cs+,Fr+), H+(aq),NH4+,Sr2+,Ba2+,Ra2+,Tl+ = soluble strontium hydroxide,
Sr(OH)2, is soluble
+ any other cation = low solubility (insoluble) silver hydroxide, AgOH, is insoluble (forms a precipitate)
Phosphate, PO43-, Carbonate, CO32-, sulphite, SO32- + alkali ions (Li+,Na+,K+,Rb+,Cs+,Fr+), H+(aq),NH4+ = soluble ammonium phosphate,
(NH4)3PO4, is soluble
+ any other cation = low solubility (insoluble) magnesium carbonate, MgCO3, is insoluble