Question

Explain when a sparingly soluble salt will precipitate from solution.

Answer 1

for example PbCl2 is sprangly soluble salt

means some amount of slat dissolve in aqueous solution to forms ions but some salt is remains as undissolved salt.

if we add common ion to such salts these sprangly soluble salt forms precipitate.

PbCl2 <-----------> Pb⁺²   + 2Cl^-

if we add NaCl to above solution

Cl^-  ions increase in the solution. so to reattain equilibrium some Cl^-  becomes precipitate by combining with Pb⁺²  .

so precipitate will form when common ion added to sprangly soluble salts.