Solubility Rules
How can I determine if a compound is soluble or a precipitate?
USE THE SOLUBILITY RULES
A) Compounds containing the following are ALWAYS SOLUBLE:
| Name | Formula |
| Nitrates | (NO3)- |
| Group 1 Metals (Alkali Family) | Li, Na, K, Rb, Cs, Fr |
| Ammonium | (NH4)+ |
| Acetate | (CH3COO)- or (C2H3O2)- |
B) Compounds containing the following are USUALLY SOLUBLE:
| Name | Formula |
| Chlorides, Bromides, Iodides** | Cl, Br, I |
|
**Exceptions to this rule include Ag, Pb, & Hg which are INSOLUBLE |
|
| Sulfates** | (SO4)-2 |
|
**Exceptions to this rule include Ca, Sr, Ba, Ag, Pb, & Hg which are INSOLUBLE |
|
C) Compounds containing the following are INSOLUBLE:
| Name | Formula |
| Hydroxides, Carbonates, Phosphates** | (OH)-, (CO3)-2, (PO4)-3 |
|
**Exceptions to this rule include (NH4)+ & Alkali Metals (Group 1) which are SOLUBLE |
|
|
Generally any other compounds are best classified as INSOLUBLE |
|
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Examples:
| COMPOUND | SOLUBLE OR INSOLUBLE | REASON |
| NaCl | Soluble | 1) Group 1
Metal (Sodium)
AND 2) Chloride (not with an exception) |
| AgI | Insoluble | Exception to Chloride Rule |
| Fe(NO3)3 | Soluble | Nitrates Soluble |
| Mg(OH)2 | Insoluble | Hydroxides Insoluble |
| KOH | Soluble | Group 1 Metals are soluble (even when with hydroxides) |
| Ca3(PO4)2 | Insoluble | Phosphates are insoluble |
Click here to access Quia to practice determining solubility:
First Quia Activity: http://www.quia.com/pop/112042.html
Second Quia Activity: http://www.quia.com/pop/111895.html