What this calculator does
The solubility rules are a short, fixed set of guidelines taught in introductory chemistry for predicting whether an ionic compound will dissolve in water, without needing a solubility-product constant or lab data. They cover the common cations and anions found in a typical high-school or first-year chemistry course, and the exceptions are well established rather than approximate.
This calculator applies the standard solubility rules to a chosen cation and anion pair, in the order chemistry courses normally teach them, so a question like "solubility rules" for a specific compound, such as silver chloride or barium sulfate, gets a direct soluble or insoluble answer along with the exact rule that decided it.
The formula
The rules are applied in priority order: Group 1 metal and ammonium compounds are always soluble regardless of anion; then nitrates and acetates are always soluble; then chlorides, bromides and iodides are soluble except with silver, lead(II) or mercury(I); then sulfates are soluble except with barium, lead(II), calcium, strontium or silver; then hydroxides, carbonates, phosphates and sulfides are insoluble except with Group 1 cations, ammonium, and (for hydroxides only) barium or strontium.
| Term | Meaning |
|---|---|
| Cation | The positively charged ion in the compound, such as sodium (Na+) or barium (Ba2+). |
| Anion | The negatively charged ion in the compound, such as chloride (Cl-) or sulfate (SO4^2-). |
| Soluble | The compound dissolves in water to a significant extent, forming a clear solution rather than a solid precipitate. |
| Insoluble | The compound does not dissolve to a significant extent, and forms a solid precipitate in water. |
The inputs explained
| Field | What to enter |
|---|---|
| Cation | Select the cation (positive ion) of the compound. |
| Anion | Select the anion (negative ion) of the compound. |
When to use it
Predicting a precipitate before mixing two solutions
When two soluble salts are mixed, a precipitate forms only if one possible product of the swapped ions is insoluble. Checking each candidate pairing against the solubility rules predicts the result before running the reaction.
Checking homework or an exam answer
The solubility rules are fixed and commonly tested; running a specific cation/anion pair through them confirms whether a written answer applied the right exception.
Working out how to separate ions from a mixed solution
Choosing a precipitating anion that is insoluble with the target cation but soluble with everything else in solution is a standard qualitative-analysis technique, and the rules decide which anion to pick.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
Is silver soluble with common anions?
The same silver cation, paired with a range of common anions.
| Anion | Prediction |
|---|---|
| Nitrate | Soluble |
| Acetate | Soluble |
| Chloride | Insoluble |
| Bromide | Insoluble |
| Iodide | Insoluble |
| Sulfate | Insoluble |
Which common cations are soluble with sulfate?
The same sulfate anion, paired with a range of common cations.
| Cation | Prediction |
|---|---|
| Sodium | Soluble |
| Magnesium | Soluble |
| Calcium | Insoluble |
| Strontium | Insoluble |
| Barium | Insoluble |
| Lead(II) | Insoluble |
Questions
Are all sodium compounds soluble?
Yes, by the solubility rules. Sodium is a Group 1 metal, and every Group 1 metal salt is treated as soluble regardless of which anion it is paired with, with no common exceptions taught at this level.
Why is silver chloride insoluble when most chlorides are soluble?
Chlorides, bromides and iodides are soluble as a general rule, but silver, lead(II) and mercury(I) are the standard named exceptions. Silver chloride is the classic example used to demonstrate this exception in a lab.
Are all carbonates insoluble?
Almost all, except for Group 1 metal carbonates and ammonium carbonate, which are soluble. Calcium carbonate, magnesium carbonate and most other metal carbonates are insoluble, which is why limestone (calcium carbonate) does not dissolve in water.
Do these rules apply to gases dissolving in water, or only to ionic solids?
Only to ionic solids (salts) dissolving in water. Gas solubility in water follows completely different rules based on partial pressure and temperature, not the ionic solubility rules used here.
For the volume and dosage side of chemistry-adjacent conversions, see the mg to mL calculator.