by marixjohn
Wednesday, January 5, 2011
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WHAT IS SOLUBILITY? Solubility is the property of a solid, liquid, or gaseous chemical substance called solute to dissolve in a liquid solvent to form a homogeneous solution. The solubility of a substance strongly depends on the used solvent as well as on temperature and pressure. The pressure also affects the solution whether it is gas or liquid, like temperature. So, in definition of solubility we always mention the pressure and temperature "fixed". The extent of the solubility of a substance in a specific solvent is measured as the saturation concentration where adding more solute does not increase the concentration of the solution.
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| Calcium Carbonate... Carbonates are insoluble unless combined with NH4+ & alkali metals |
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| Sodium metal with oxide layer. An alkali metal that is soluble. |
SOLUBILITY RULES-SOLUBLES-
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.)
Alkali metals (green)
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.
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| Ammonium salt |
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).
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.).
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| Copper sulfate |
-INSOLUBLES-
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)
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| Aluminum hydroxide |
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).
Rule 8. All sulfites (SO3=), carbonates (CO3=), chromates (CrO4=), and phosphates (PO43-) are insoluble 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).
SOLUBLE AND INSOLUBLE SUBSTANCES IN WATER Water is an excellent solvent for many compounds. Some dissolve in it as molecules while others, called electrolytes, dissociate and dissolve not as neutral molecules but as charged species called ions. Compounds which exist as solid ionic crystals dissolve in water as ions, and most of them are highly soluble in water.
Some ionic compounds dissolve in water, which arises because of the attraction between positive and negative charges. For example, the salt's positive ions (e.g. Ag+) attract the partially-negative oxygens in H2O. Likewise, the salt's negative ions (e.g. Cl−) attract the partially-positive hydrogens in H2O. Note: oxygen is partially-negative because it is more electronegative than hydrogen, and vice-versa.
VIDEOS/SONGS about SOLUBILITY RULES:Lyrics:
Dissolve this
Dissolve this
Dissolve this
Ni ni ni ni nitrate and acetate
Perchlorate and even chlorate
Always are soluble
No exceptions to that rule
What else? theres ammonium
Plus the el-ments in group 1 plus charge. And such
There are salts that water cant touch
Carbonate, chromate
Oxalate and phosphate
Remember sulfides
Dont forget hydroxides. (while its rollin)
Hold on! But some salts are soluble
Like that:
Like that:
But with metals, its too much
These are salts and metals, uh, you cant touch
Dissolve this
Dissolve this
Dissolve this
Dissolve this
Dissolve this
Dissolve this
Ni ni ni ni nitrate and acetate
Perchlorate and even chlorate
Always are soluble
No exceptions to that rule
What else? theres ammonium
Plus the el-ments in group 1 plus charge. And such
There are salts that water cant touch
Carbonate, chromate
Oxalate and phosphate
Remember sulfides
Dont forget hydroxides. (while its rollin)
Hold on! But some salts are soluble
Like that:
Like that:
But with metals, its too much
These are salts and metals, uh, you cant touch
Dissolve this
Dissolve this
Dissolve this
SOLUBILITY SONG from Cronell University,
Chemistry Department
another SOLUBILITY SONG
EVALUATION:
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