CHEM 1150: Solubility Rules & Polyatomic Ions

Rule 1

compounds containing Li⁺, Na⁺, K⁺, Rb⁺, and Cs⁺ (group 1 metals) and NH⁺₄ are soluble (will dissolve & give ions in water)

Rule 2

compounds with nitrate (NO₃^-), perchlorate (ClO₄^-) and acetate (CH₃CO^-₂) are soluble

Rule 3

compounds with Ag⁺, Pb²⁺, and Hg²⁺₂ are insoluble (will form a solid/precipitate) except for those with anions from rule 2

Rule 4

compounds with Cl^-, Br^-, and I^- are soluble (except for those with cations from rule 3)

Rule 5

compounds with carbonate (CO^2-₃), phosphate (PO^3-₄), sulfide (S^2-), oxide (O^2-), and hydroxide (OH^-) are insoluble (except for those with cations from rule 1

exception: Ba²⁺ with OH^- is soluble

Rule 6

compounds with sulfate (SO^2-₄) are soluble (except for rule 3 cations and Ca²⁺, Sr²⁺, and Ba²⁺)

Rule 7

most other iconic compounds are insoluble

Ammonium

NH⁺₄

Hydronium

H₃O⁺

Hydroxide

OH^-

Acetate

CH₃COO^- or C₂H₃O₂

Cyanide

CN^-

Perchlorate

ClO^-₄

Chlorate

ClO₃^-

Chlorite

ClO^-₂

Hypochlorite

ClO^-

Nitrate

NO₃^-

Nitrite

NO^-₂

Sulfate

SO₄^2-

Sulfite

SO₃^2-

Carbonate

CO₃^2-

Bicarbonate

HCO₃^-

Phosphate

PO^3-₄

Chromate

CrO^2-₄

Dichromate

Cr₂O^2-₇

Permanganate

MnO₄^-