Answer to Question #111150 in General Chemistry for mya 19

Question

Sodium sulfate is slowly added to a solution containing 0.0500 M Ca2+(aq) and 0.0290 M Ag+(aq) .

What will be the concentration of Ca2+(aq) when Ag2SO4(s) begins to precipitate?

What percentage of the Ca2+(aq) can be precipitated from the Ag+(aq) by selective precipitation?

Answer 1

K_sp(Ag₂SO₄)=[Ag⁺]²[SO4^2-]=1.2*10^-5

K_sp(CaSO₄)=[Ca²⁺][SO₄^2-]=2.4*10^-5

Ag2SO4-->2Ag⁺ + SO₄^2-

CaSO4-->Ca²⁺+SO₄^2-

 Ag2SO4(s) begins to precipitate when is more than [SO₄^2-]=1.2*10^-5/[Ag+]² = 0.0143 M;

If [SO42-]=0.0143 M, then [Ca2+]=2.4*10^-5/0.0143=0.0016783 M