Solubility chart and solubility rules for ionic compounds
The chart shows whether common ionic compounds dissolve in water at about 25 °C. Use it with the solubility rules below to predict which reactions form a precipitate.
| NH₄⁺ | Na⁺ | K⁺ | Mg²⁺ | Ca²⁺ | Ba²⁺ | Al³⁺ | Fe²⁺ | Fe³⁺ | Cu²⁺ | Zn²⁺ | Ag⁺ | Pb²⁺ | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| NO₃⁻ | S | S | S | S | S | S | S | S | S | S | S | S | S |
| Cl⁻ | S | S | S | S | S | S | S | S | S | S | S | I | sS |
| SO₄²⁻ | S | S | S | S | sS | I | S | S | S | S | S | sS | I |
| CO₃²⁻ | S | S | S | I | I | I | – | I | – | I | I | I | I |
| OH⁻ | S | S | S | I | sS | S | I | I | I | I | I | – | I |
| PO₄³⁻ | S | S | S | I | I | I | I | I | I | I | I | I | I |
| S²⁻ | S | S | S | – | – | – | – | I | I | I | I | I | I |
| CH₃COO⁻ | S | S | S | S | S | S | S | S | S | S | S | sS | S |
Rules of thumb at about 25 °C. Nitrates, acetates and group 1 and ammonium salts are almost always soluble.
How to read the chart
Positive ions (cations) run across the top and negative ions (anions) run down the side. The box where a row and a column meet describes the compound of those two ions, colored by the legend: soluble, slightly soluble, insoluble, or reacts with water / does not exist. Aluminum carbonate, for example, cannot be made in water because it breaks down into aluminum hydroxide and carbon dioxide.
The solubility rules
All nitrates are soluble, and so are nearly all acetates; silver acetate is only slightly soluble. Sodium, potassium and ammonium salts are always soluble, as are nearly all other group 1 salts.
Chlorides are soluble except silver chloride, which is insoluble, and lead(II) chloride, which is slightly soluble. Sulfates are soluble except barium sulfate and lead(II) sulfate, which are insoluble, and calcium sulfate and silver sulfate, which are slightly soluble.
Carbonates, phosphates and sulfides are insoluble or break down in water unless they contain sodium, potassium or ammonium. Most hydroxides are insoluble too; the exceptions are sodium, potassium, ammonium and barium hydroxides, which are soluble, and calcium hydroxide, which is slightly soluble.
Worked example: predicting a precipitate
What happens when silver nitrate solution is mixed with sodium chloride solution? Swap the partners to find the possible products: silver chloride (AgCl) and sodium nitrate (NaNO₃). Sodium nitrate is soluble, but silver chloride is insoluble, so a white precipitate forms. The net ionic equation is Ag⁺(aq) + Cl⁻(aq) → AgCl(s). If both possible products are soluble, as when sodium chloride is mixed with potassium nitrate, no precipitate forms.
Limits of the chart
Solubility changes with temperature, and insoluble never means zero: a tiny amount of every salt dissolves. The chart is a set of rules of thumb for room temperature, not exact measurements.
FAQ
Is AgCl soluble in water?
No. Silver chloride is insoluble, which is why a white precipitate appears when silver nitrate is added to a solution containing chloride ions. This reaction is the standard test for chloride.
Is BaSO₄ soluble in water?
No, barium sulfate is insoluble. So little dissolves that patients can swallow it safely as a contrast agent for X-rays, even though dissolved barium ions are toxic.
Is CaCO₃ soluble in water?
Calcium carbonate is insoluble in pure water, but it dissolves in acids and releases carbon dioxide. Rainwater containing dissolved carbon dioxide slowly dissolves limestone, which is how many caves form.
What does slightly soluble mean?
A slightly soluble compound dissolves only a little. A common rule of thumb calls a compound soluble above about 1 g per 100 mL of water, slightly soluble between 0.1 and 1 g, and insoluble below 0.1 g, though textbooks draw these lines differently.