Solubility Rules

Always Soluble: 

• Alkali Metals (Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺)

• Ammonium (NH₄⁺)

• Nitrates (NO₃⁻)

Generally Soluble: 

• Halides (Cl⁻, Br⁻, I⁻): Generally soluble, but insoluble with lead (Pb²⁺), mercury (Hg₂²⁺), and silver (Ag⁺). Fluorides (F⁻) are less predictable.

• Sulfates (SO₄²⁻): Generally soluble, but insoluble with calcium (Ca²⁺), barium (Ba²⁺), strontium (Sr²⁺), lead (Pb²⁺), and mercury (Hg₂²⁺).

Assume Insoluble: 

• All other compounds unless they contain the always soluble ions. 

AP Chemistry Baseline: Na⁺, K⁺, NH₄⁺, NO₃⁻ are always soluble.