3.10 Solubility

Solubility Rules and Polyatomic Ions

Polyatomic Ions

Ions composed of multiple atoms that carry a charge.

Hydroxide

A polyatomic ion (OH-) that carries a negative charge.

Hydronium

A polyatomic ion (H3O+) that carries a positive charge.

Ammonia

A compound (NH3) composed of one nitrogen atom and three hydrogen atoms.

Ammonium

A polyatomic ion (NH4+) that carries a positive charge.

Carbonate

A polyatomic ion (CO32-) that carries a negative charge.

Nitrate

A polyatomic ion (NO3-) that carries a negative charge.

Phosphate

A polyatomic ion (PO43-) that carries a negative charge.

Arsonate

A polyatomic ion (AsO43-) that carries a negative charge.

Sulfate

A polyatomic ion (SO42-) that carries a negative charge.

Selenium

A polyatomic ion (SeO42-) that carries a negative charge.

Chlorate

A polyatomic ion (ClO3-) that carries a negative charge.

Bromate

A polyatomic ion (BrO3-) that carries a negative charge.

Acetate

A polyatomic ion (C2H3O2- or CH3COO-) that carries a negative charge.

Solubility Rules

Guidelines used to predict the solubility of compounds in water.

Group 1 metals

Elements in the first group of the periodic table (e.g., sodium, potassium) that form soluble compounds.

Nitrate

A polyatomic ion (NO3-) that always forms soluble compounds.

Acetate compounds

Compounds containing the acetate ion are assumed to be soluble.

Pb, Ag, and Hg

Lead, silver, and mercury are elements that form insoluble salts.

F- salts

Salts containing fluoride ions are also insoluble.

Halogens

Elements in the halogen group (Cl, Br, I) that form soluble salts.

Hydroxide compounds

Compounds containing the hydroxide ion are generally insoluble, except for strontium, barium, and radium compounds.

Other salts

The majority of salts are insoluble in water unless specified otherwise.