A solution contains Ca²⁺ and Pb²⁺ ions, both at a concentration of 0.010 M. You wish to separate the two ions from each other as completely as possible by precipitating one but not the other using aqueous Na₂SO₄ as the precipitating agent.
(a) Which will precipitate first as sodium sulfate is added, CaSO₄ or PbSO₄?
(b) What will be the concentration of the first ion that precipitates (Ca²⁺ or Pb²⁺) when the second, more soluble salt begins to precipitate?