Question

Which of the following salts would be more soluble in acid solution than in pure water?

PbBr₂

AgNO₃

SrCl₂

AgI

Please provide a thorough explanation as I was absent during this lecture... Thank you!!

Answer 1

The secret to these is knowing what anions react with H^+ (the acid) and if any weak acids or precipitates are formed. Another way to view this is to tate a general rule: the solubility of slightly soluble salts containing basic anions increases as [H⁺] increases (as pH is lowered). if the anion of a salt is basic, it will react with any H⁺ in solution, and be removed from the equilibrium. by LeChatelier's principle, the equilibrium will move to replace the product; in the case of the equilibrium between undissolved solid and ions, this will result in more of the solid dissolving and an increase in the solubility of the solid.

In other words, if the anion of the salt can react with H+ and produce a strong acid it will not be more soluble in acid. We need a weak acid. so for this compounds:

PbBr2, the anion Br- can form HBr which is a strong acid, so it's not more soluble in acid.
AgNO3, the anion NO3- form the HNO3 a strong acid, not more soluble.
SrCl2, the anion Cl- form the HCl a strong acid, not more soluble.
AgI, the anion I- form the HI, a slightly strong acid, this could be more soluble in acid.
BaSO3, the anion SO3 2- form the HSO3- a weak acid, this is more soluble in acid.

Hope this helps