how does pH affect solubility?

Answer 1

Depends on the solute -- in an acidic solvent, an alkaline solute will generally be more soluble, and vice versa.

Of course, that doesn't universally apply. For example, Calcium hydroxide (water soluble and very alkaline) will react with sulfuric acid to make calcium sulfate (low solubility; Ksp = 4.93x10^-5).

But there are also some low solubility salts that, upon addition of more acid (reducing the pH) become more soluble. Others can become more soluble with the addition of base (increasing the pH).

It's all rather confusing, really.