Solubility Rules

rules for determining a compounds solubility based on the ions it contains

1) Always Soluble

Li⁺, Na⁺, K⁺, NH₄⁺, NO₃⁻, C₂H₃O₂⁻

2) Never Soluble (if not 1)

Pb²⁺, CO₃²⁻, PO₄³⁻

3) Soluble unless Pb²⁺, Ag⁺, Hg₂²⁺

Cl⁻, Br⁻, I⁻ (halogens)

4) Ca²⁺, Sr²⁺, Ba²⁺ Reverse These Rules (+ 1 and 2)

I. SO₄²⁻ is usually soluble

II. S²⁻ is usually insoluble

III. OH⁻ is usually insoluble, reverses to slightly soluble