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Solubility Rules Reference
Check the standard solubility rules for common ions, including the exceptions that decide whether a precipitate forms in a reaction.
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Math & Science
Solubility Rules Reference
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Solubility
BaSO₄ is insoluble: sulfates are generally soluble, but barium, lead, calcium, and strontium sulfates are the standard exceptions.
How the Solubility Rules Reference works
- Enter the compound or select the anion you are working with.
- Read the general rule and, more importantly, its exceptions — the exceptions are where exam questions and real precipitates live.
- Use the result to predict whether mixing two solutions produces a precipitate.
FAQ
Which rules have no exceptions worth remembering?
Nitrates and Group 1 salts are reliably soluble, and ammonium salts nearly always are. Almost every other rule carries exceptions you have to know.
Why do the exceptions matter so much?
Because precipitation reactions are defined by them. Sulfates being soluble is unremarkable; barium sulfate being insoluble is the basis of a standard test.
Is insoluble truly zero solubility?
No. Insoluble means very low solubility, quantified properly by the solubility product. The rules are a rapid qualitative shortcut, not a substitute for Ksp.
How we compare
| Feature | Online Tool Store | A graphing calculator | A stats package |
|---|---|---|---|
| Exceptions listed with each rule | ✓ | ✓ | Varies |
| Searchable by compound | ✓ | ✗ | ✓ |
| No login | ✓ | ✓ | ✗ |
| Ksp values | ✗ | ✓ | ✓ |
Solubility Rules Reference puts the exceptions next to each rule, because the exceptions are what actually determine whether a precipitate appears.