1.
Salts containing Group I elements are soluble (Li+, Na+,
K+, Cs+, Rb+). Exceptions to this rule are
rare.
Salts containing the ammonium ion (NH4+) are also soluble.
2. Salts containing nitrate ion (NO3-) are generally soluble.
3. Salts containing Cl -, Br -, I - are generally soluble. Important exceptions to this rule are halide salts of
Ag+, Pb2+, and (Hg2)2+. Thus, AgCl, PbBr2, and Hg2Cl2 are all insoluble.
4. Most silver salts are insoluble. AgNO3 and Ag(C2H3O2) are common soluble salts of silver; virtually
anything else is insoluble.
5. Most sulfate salts are soluble. Important exceptions to this rule include BaSO4, PbSO4, Ag2SO4 and
SrSO4 .
6. Most hydroxide salts are only slightly soluble. Hydroxide salts of Group I elements are soluble.
Hydroxide salts of Group II elements (Ca, Sr, and Ba) are slightly soluble. Hydroxide salts of transition
metals and Al3+ are insoluble. Thus, Fe(OH)3, Al(OH)3, Co(OH)2 are not soluble.
7. Most sulfides of transition metals are highly insoluble. Thus, CdS,FeS , ZnS, Ag2S are all insoluble.
Arsenic, antimony, bismuth, and lead sulfides are also insoluble.
8. Carbonates are frequently insoluble. Group II carbonates (Ca, Sr, and Ba) are insoluble. Some other
insoluble carbonates include FeCO3 and PbCO3.
9. Chromates are frequently insoluble. Examples: PbCrO4, BaCrO4
10. Phosphates are frequently insoluble. Examples: Ca3(PO4)2, Ag3PO4
11. Fluorides are frequently insoluble. Examples: BaF2, MgF2 PbF2.
Salts containing the ammonium ion (NH4+) are also soluble.
2. Salts containing nitrate ion (NO3-) are generally soluble.
3. Salts containing Cl -, Br -, I - are generally soluble. Important exceptions to this rule are halide salts of
Ag+, Pb2+, and (Hg2)2+. Thus, AgCl, PbBr2, and Hg2Cl2 are all insoluble.
4. Most silver salts are insoluble. AgNO3 and Ag(C2H3O2) are common soluble salts of silver; virtually
anything else is insoluble.
5. Most sulfate salts are soluble. Important exceptions to this rule include BaSO4, PbSO4, Ag2SO4 and
SrSO4 .
6. Most hydroxide salts are only slightly soluble. Hydroxide salts of Group I elements are soluble.
Hydroxide salts of Group II elements (Ca, Sr, and Ba) are slightly soluble. Hydroxide salts of transition
metals and Al3+ are insoluble. Thus, Fe(OH)3, Al(OH)3, Co(OH)2 are not soluble.
7. Most sulfides of transition metals are highly insoluble. Thus, CdS,
Arsenic, antimony, bismuth, and lead sulfides are also insoluble.
8. Carbonates are frequently insoluble. Group II carbonates (Ca, Sr, and Ba) are insoluble. Some other
insoluble carbonates include FeCO3 and PbCO3.
9. Chromates are frequently insoluble. Examples: PbCrO4, BaCrO4
10. Phosphates are frequently insoluble. Examples: Ca3(PO4)2, Ag3PO4
11. Fluorides are frequently insoluble. Examples: BaF2, MgF2 PbF2.
Here is another source covering the same rules with examples:
Rule 1. All compounds of Group IA elements (the alkali metals) are soluble.
For example, NaNO3, KCl, and LiOH are all soluble compounds. This means that an aqueous solution of KCl really contains the predominant species K+ and Cl- and, because KCl is soluble, no KCl is present as a solid compound in aqueous solution:
KCl(s) => K+(aq.) + Cl-(aq.)
KCl(s) => K+(aq.) + Cl-(aq.)
Rule 2. All ammonium salts (salts of NH4+) are soluble.
For example, NH4OH is a soluble compound. Molecules of NH4OH completely dissociate to give ions of NH4+ and OH- in aqueous solution.
Rule 3. All nitrate (NO3-), chlorate (ClO3-), perchlorate (ClO4-), and acetate (CH3COO- or C2H3O2-, sometimes abbreviated as Oac-) salts are soluble.
For example, KNO3 would be classified as completely soluble by rules 1 and 3. Thus, KNO3 could be expected to dissociate completely in aqueous solution into K+ and NO3- ions: KNO3 => K+(aq.) + NO3-(aq.)
Rule 4. All chloride (Cl-), bromide (Br-), and iodide (I-) salts are soluble except for those of Ag+, Pb2+, and Hg22+.
For example, AgCl is a classic insoluble chloride salt:
AgCl(s) <=> Ag+(aq.) + Cl-(aq.) (Ksp = 1.8 x 10-10).
AgCl(s) <=> Ag+(aq.) + Cl-(aq.) (Ksp = 1.8 x 10-10).
Rule 5. All sulfate ( SO4=) compounds are soluble except those of Ba2+, Sr2+, Ca2+, Pb2+, Hg22+, and Hg2+, Ca2+ and Ag+ sulfates are only moderately soluble.
For example, BaSO4 is insoluble (only soluble to a very small extent):
BaSO4(s) <=> Ba2+(aq.) + SO42-(aq.) (Ksp = 1.1 x 10-10).
Na2SO4 is completely soluble:
Na2SO4(s) => 2 Na+(aq.) + SO42-(aq.).
BaSO4(s) <=> Ba2+(aq.) + SO42-(aq.) (Ksp = 1.1 x 10-10).
Na2SO4 is completely soluble:
Na2SO4(s) => 2 Na+(aq.) + SO42-(aq.).
Rule 6. All hydroxide (OH-) compounds are insoluble except those of Group I-A (alkali metals) and Ba2+, Ca2+, and Sr2+.
For example, Mg(OH)2 is insoluble (Ksp = 7.1 x 10-12).
NaOH and Ba(OH)2 are soluble, completely dissociating in aqueous solution:
NaOH(s) => Na+(aq.) + OH-(aq.), a strong base
Ba(OH)2(s) => Ba2+(aq.) + 2OH-(aq.) (Ksp = 3 x 10-4)
NaOH and Ba(OH)2 are soluble, completely dissociating in aqueous solution:
NaOH(s) => Na+(aq.) + OH-(aq.), a strong base
Ba(OH)2(s) => Ba2+(aq.) + 2OH-(aq.) (Ksp = 3 x 10-4)
Rule 7. All sulfide (S2-) compounds are insoluble except those of Groups I-A and II-A (alkali metals and alkali earths).
For example, Na2S(s) <=> 2Na+(aq.) + S2-(aq.)
MnS is insoluble (Ksp = 3 x 10-11).
MnS is insoluble (Ksp = 3 x 10-11).
Rule 8. All sulfites (SO3=), carbonates (CO3=), chromates (CrO4=), and phosphates (PO43-) areinsoluble except for those of NH4+ and Group I-A (alkali metals)(see rules 1 and 2).
For example, calcite, CaCO3(s) <=> Ca2+(aq.) + CO3=(aq.) (Ksp = 4.5 x 10-9).
**ADDITIONAL SOURCES**
Website explaining the rules: http://www.chem.sc.edu/faculty/morgan/resources/solubility/
Here are some flashcards: https://quizlet.com/232395/solubility-rules-practice-flash-cards/
Here's a helpful song: https://www.youtube.com/watch?v=VJoKQ3ULCVs
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