| Rules for Learning the Solubility of Ionic Compounds in Water
Negative Ions
(Anions)
| +
| Positive Ions
(Cations)
| =
| Solubility of compounds in water
| Example
|
| any anion
| +
| alkali ions
(Li+,Na+,K+,Rb+,Cs+,Fr+)
| =
| soluble
| sodium fluoride, NaF, is soluble
|
| any anion
| +
| hydrogen ion
[H+(aq)]
| =
| soluble
| sodium hydride, NaH, is soluble
|
| any anion
| +
| amonium ion
(NH4+)
| =
| soluble
| ammonium chloride, NH4Cl, is soluble
|
nitrate
NO3-
| +
| any cation
| =
| soluble
| potassium nitrate, KNO3, is soluble
|
acetate
(CH3COO-)
| +
| any cation
| =
| soluble
| sodium acetate, CH3COONa, is soluble
|
| Chloride (Cl-), Bromide (Br-), Iodide (I-)
| +
| silver (Ag+), lead (Pb2+), mercury (Hg2+), copper (Cu+), thallium (Tl+)
| =
| low solubility (insoluble)
| silver chloride, AgCl, forms a white precipitate (a white solid)
|
| +
| any other cation
| =
| soluble
| potassium bromide, KBr, is soluble
|
Suphate
(SO42-)
| +
| calcium (Ca2+), strontium (Sr2+), barium (Ba2+), silver (Ag+), lead (Pb2+), radium (Ra2+)
| =
| low solubility (insoluble)
| barium sulphate, BaSO4, forms a white precipitate (a white solid)
|
| +
| any other cation
| =
| soluble
| copper sulphate, CuSO4, is soluble
|
Sulfide
S2-
| +
| alkali ions (Li+,Na+,K+,Rb+,Cs+,Fr+), alkali earth metals (Be2+,Mg2+,Ca2+,Sr2+,Ba2+,Ra2+),
and H+(aq), NH4+
| =
| soluble
| magnesium sulfide, MgS, is soluble
|
| +
| any other cation
| =
| low solubility (insoluble)
| zinc sulfide, ZnS, is insoluble
|
Hydroxide
OH-
| +
| alkali ions (Li+,Na+,K+,Rb+,Cs+,Fr+), H+(aq),NH4+,Sr2+,Ba2+,Ra2+,Tl+
| =
| soluble
| strontium hydroxide,
Sr(OH)2, is soluble
|
| +
| any other cation
| =
| low solubility (insoluble)
| silver hydroxide, AgOH, is insoluble (forms a precipitate)
|
| Phosphate, PO43-, Carbonate, CO32-, sulphite, SO32-
| +
| alkali ions (Li+,Na+,K+,Rb+,Cs+,Fr+), H+(aq),NH4+
| =
| soluble
| ammonium phosphate,
(NH4)3PO4, is soluble
|
| +
| any other cation
| =
| low solubility (insoluble)
| magnesium carbonate, MgCO3, is insoluble
|
-
All compounds of the ammonium ion (NH4+), and of Alkali metal (Group IA) cations, are soluble.
- All nitrates and acetates (ethanoates) are soluble.
- All chlorides, bromides and iodides are soluble EXCEPT those of silver, lead and mercury(I).
- All sulphates are soluble EXCEPT those of silver, lead, mercury(I), barium, strontium and calcium.
- All carbonates, sulfites and phosphates are insoluble EXCEPT those of ammonium and Alkali metal (Group IA) cations.
- All hydroxides are insoluble EXCEPT those of ammonium, barium and alkali metal (Group I) cations.
- All sulfides are insoluble EXCEPT those of ammonium, Alkali metal (GroupI) cations and Alkali earth metal (Group II) cations.
- All oxides are insoluble EXCEPT those of calcium, barium and Alkali metal (Group I) cations; these soluble ones actually react with the water to form hydroxides (hydrolyse).
|
