[gambit]

When adding K₃PO₄ to H₂O the pH goes basic, What is the reaction that explains the pH change? What about when adding AlCl₃, or KNO₃.

For the AlCl₃ salt would it make sense to write the reaction HCL -> H⁺ + Cl^-?

[Arkcon]

There is, unfortunately, a different answer in each case, it depends on our different definitions of acid and base.  Let me link you to the wikipedia page, and you can try to see how you can pull together an answer, for each case, and any other case you might encounter on the exam:

http://en.wikipedia.org/wiki/Acid%E2%80%93base_reaction#Arrhenius_definition

http://en.wikipedia.org/wiki/Br%C3%B8nsted-Lowry_acid-base_theory

[gambit]

Well what I initially did, was write out all of the reactions, for example:
   2AlCl₃ + 6H₂O -> 2Al(OH)₃ + 3HCL

The teacher said, this reaction is correct, but it was not the reaction he was looking for.
So to write the reaction that determines the pH, would I just write the net-ionic for the cation or anion that is strong. So the AlCl₃ has the cation Al which would make Al(OH)₃, and the anion Cl which would make HCL. Since the HCL is the strong one, then would i provide HCl -> H⁺ + Cl^-

[Borek]

Well what I initially did, was write out all of the reactions, for example:
   2AlCl₃ + 6H₂O -> 2Al(OH)₃ + 3HCL

The teacher said, this reaction is correct, but it was not the reaction he was looking for.
So to write the reaction that determines the pH, would I just write the net-ionic for the cation or anion that is strong. So the AlCl₃ has the cation Al which would make Al(OH)₃, and the anion Cl which would make HCL. Since the HCL is the strong one, then would i provide HCl -> H⁺ + Cl^-

Go net ionic, one of the ions is only a spectator and as such has nothing to do with the pH change.

To add to Arkcon links:

http://www.chembuddy.com/?left=pH-calculation&right=bronsted-lowry-theory