solubility rules

• Rule 1: All ionic compounds containing: group 1 ions (Li+, Na+, K+, Rb+, Cs+ & Fr+), ammonium (NH4+), ethanoate/acetate (CH3COO–), nitrate (NO3–), and nitrite (NO2–), and acids are soluble.

  Note: This rule takes higher priority over other rules.
• Rule 2: All ionic compounds containing: chlorides (Cl–), bromides (Br–) & iodides (I–) are soluble, except when they combine with: silver (Ag+), lead (II) (Pb2+) or mercury (II) (Hg2+), they are insoluble.

  • Note: lead (II) chloride (PbCl2) is moderately soluble in hot water
• Rule 3: All ionic compounds containing sulfates (SO4 2–) are soluble, except when it is combined with: silver (Ag+), lead (II) (Pb2+), mercury (II) (Hg2+), calcium (Ca2+), strontium (Sr2+) and barium (Ba2+), it is insoluble.
• Rule 4: All ionic compounds containing: hydroxides (OH–) and oxides (O2–) are insoluble, except when they combine with: ammonium (NH4+), sodium (Na+), potassium (K+) and barium (Ba2+), they are soluble.
• Rule 5: All ionic compounds containing: carbonates (CO3 2–), phosphates (PO4 3–) and sulfides (S 2–) are insoluble, except when they combine with: ammonium (NH4+), sodium (Na+) and potassium (K+), they are soluble.
• Rule 6: Slightly soluble is considered as insoluble.
• Rule 7: Most of the ionic compounds that are not listed may assumed to be insoluble.