Solubility

Saw a friend’s post. What makes a salt soluble in water? Like charges. Like dissolves like. Namely, group 1 elements are most commonly found on earth as ions. Group I elements are also found commonly bonded to the other far end of the periodic table, reflecting on the ionic character of the bond. They are always soluble in water. Likewise, their partners, the halogens (in the form of halogen metals) are found to be soluble.

NH4+ almost always exists as a positive ion, so they’re soluble.

NO3, CH3OO, Chlorates are grouped together in terms of solubility (they’re almost always soluble), because of their acid-base chemistry relations . They’re conjugate bases of relatively strong acids (nitric acid, chloric acid, acetic acid) -- that is, once they lose the H+/proton, it's not going to grab it back, so it's going to stay in the anion form.

Silver, mercury, and lead compounds are generally insoluble.
Sulfates (SO4^2-) are generally soluble unless they’re paired with group 2 elements (a perfect marriage).

For polyprotic acids, the doubly loss of H+ in carbonic acid and triply loss of H+ in phosphoric acid leads to insoluble carbonates and phosphates. Their acid form is soluble. Their salt forms are insoluble.

(OH^-1),hydroxides with group 1 is soluble. (OH^-1) with group 2 is slightly. (OH^-1) with (groups 3+)/metals are insoluble. Likewise with (S^2-), sulfides.

Why do they teach the solubility table in general chemistry? It’s meant to reflect on the trends of the periodic table, a direct application of it, but most teachers are neglect that fact. This leads students to learn by memorization, without rhyme or reason – even puzzled at why they’re learning it. Rules?
The ends of the periodic table are soluble.
Most acids are soluble unless they’re doubly/triply deprotonated,
sulfates make a perfect marriage with group 2. that even water can’t break
silver, mercury, and lead are generally insoluble.
(hidden rule: solubility increases when acids are added)

Physical chemistry actually doesn't add more to this general chemistry knowledge. Physical chem or at least the year course of it, only studies salts that are slightly soluble, and neglects ion-pairing effects. What you learn is the role of activities, ionic activity (the salt effect which reduces gamma, increases solubility), and the common-ion effect which drives down solubility. You can read more about it here:
http://en.wikipedia.org/wiki/Solubility_equilibrium