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I have always wanted to make a thread for this because I never understood this until NOW: Solubility rules are pretty important for those who want to get a good score on the gchem section because I believe those will be the trickiest on the test...they have to do with acidity, solubility, etc...
Here they are, first the basic rules:
1) Any alkali metal cations and ammonium (NH4+) ion are soluble
2) All compounds containing NO3-, ClO4-, ClO3-, and C2H3O2- anions are soluble.
3) All chlorides, bromides, and iodides are soluble except those containing Ag+, Pb2+, or Hg2^2+.
4) All sulfates are soluble except those containing Hg22+, Pb2+, Sr2+, Ca2+, or Ba2+.
5) All hydroxides are insoluble except compounds of the alkali metals, and Ca2+, Sr2+, and Ba2+.
6) All compounds containing PO43-, S2-, CO32-, and SO32- ions are insoluble except those that also contain alkali metals or NH4+.
Let me give an example of an important question that was posted yesterday that has to do with acidity...
ex) Why are FeCl3 and AlCl3 acidic in water?
To answer this question we would first have to know how these react with water, they both form hydroxides that are bound to the metals Fe and Al (FeOH3 and AlOH3). Now from our rules we know hydroxides are insoluble and therefore both the hydroxides will precipitate in solution. Since we reacted OH- from water we have another H+ left, this will most definitely be in solution causing it to be ACIDIC!!! The OH- ion will not be in solution because it is not soluble and will precipitate not forming a base. Definition of an Arehnius base is one that gives up OH- in solution, but the metals hydroxides can not...I like this question it really tests your knowledge...
Anyone that knows anymore rules post em up, thanks...
Here they are, first the basic rules:
1) Any alkali metal cations and ammonium (NH4+) ion are soluble
2) All compounds containing NO3-, ClO4-, ClO3-, and C2H3O2- anions are soluble.
3) All chlorides, bromides, and iodides are soluble except those containing Ag+, Pb2+, or Hg2^2+.
4) All sulfates are soluble except those containing Hg22+, Pb2+, Sr2+, Ca2+, or Ba2+.
5) All hydroxides are insoluble except compounds of the alkali metals, and Ca2+, Sr2+, and Ba2+.
6) All compounds containing PO43-, S2-, CO32-, and SO32- ions are insoluble except those that also contain alkali metals or NH4+.
Let me give an example of an important question that was posted yesterday that has to do with acidity...
ex) Why are FeCl3 and AlCl3 acidic in water?
To answer this question we would first have to know how these react with water, they both form hydroxides that are bound to the metals Fe and Al (FeOH3 and AlOH3). Now from our rules we know hydroxides are insoluble and therefore both the hydroxides will precipitate in solution. Since we reacted OH- from water we have another H+ left, this will most definitely be in solution causing it to be ACIDIC!!! The OH- ion will not be in solution because it is not soluble and will precipitate not forming a base. Definition of an Arehnius base is one that gives up OH- in solution, but the metals hydroxides can not...I like this question it really tests your knowledge...
Anyone that knows anymore rules post em up, thanks...
