General Rules for Solubility of Ionic Compounds in Water

Vocabulary flashcards detailing the general solubility rules for common ionic compounds (salts) in water at 25 °C and their notable exceptions.

Nitrate Salts ($\text{NO}_3^-$)

A class of ionic compounds where most salts are soluble in water at $25\,^\circ\text{C}$.

Salts of $\text{Na}^+$, $\text{K}^+$, and $\text{NH}_4^+$

Soluble ionic compounds containing sodium, potassium, or ammonium cations, of which most are soluble in water at $25\,^\circ\text{C}$.

Chloride Salts

Ionic compounds where most salts are soluble in water at $25\,^\circ\text{C}$, with notable insoluble exceptions being $\text{AgCl}$, $\text{PbCl}_2$, and $\text{Hg}_2\text{Cl}_2$.

Exceptions to Chloride Solubility

The chloride salts that are insoluble or precipitate: $\text{AgCl}$, $\text{PbCl}_2$, and $\text{Hg}_2\text{Cl}_2$.

Sulfate Salts

Ionic compounds where most salts are soluble in water at $25\,^\circ\text{C}$, with notable exceptions being $\text{BaSO}_4$, $\text{PbSO}_4$, and $\text{CaSO}_4$.

Exceptions to Sulfate Solubility

The sulfate salts that do not follow the general rule of solubility: $\text{BaSO}_4$, $\text{PbSO}_4$, and $\text{CaSO}_4$.

Hydroxide Compounds

Compounds where most are only slightly soluble, with $\text{NaOH}$ and $\text{KOH}$ as soluble exceptions, and $\text{Ba(OH)}_2$ and $\text{Ca(OH)}_2$ as moderately soluble.

Exceptions to Hydroxide Insolubility

$\text{NaOH}$ and $\text{KOH}$ (important soluble exceptions), along with $\text{Ba(OH)}_2$ and $\text{Ca(OH)}_2$ (moderately soluble).

Sulfide ($\text{S}^{2-}$), Carbonate ($\text{CO}_3^{2-}$), and Phosphate ($\text{PO}_4^{3-}$) Salts

Categories of ionic compounds where most salts are only slightly soluble in water at $25\,^\circ\text{C}$.

Insoluble and Slightly Soluble

Terms treated as meaning the same thing: such a tiny amount of the compound dissolves that it is not possible to detect it with the naked eye.