1)Sodium sulfate is slowly added to a solution containing 0.0500 M Ca2 (aq) and
ID: 490249 • Letter: 1
Question
1)Sodium sulfate is slowly added to a solution containing 0.0500 M Ca2 (aq) and 0.0220 M Ag (aq). What will be the concentration of Ca2 (aq) when Ag2SO4(s) begins to precipitate? Solubility-product constants, Ksp, can be found here.(1.20x10^-5)
What percentage of the Ca2 (aq) can be precipitated from the Ag (aq) by selective precipitation?
2) Suppose a solution contains 0.24 M Pb2 and 0.49 M Al3 . Calculate the pH range that would allow Al(OH)3 to precipitate but not Pb(OH)2. The Ksp values for Al(OH)3 and Pb(OH)2 can be found here.
Explanation / Answer
1)
Ag2SO4 ---------------> 2 Ag+ + SO42-
0.0220 S
Ksp = [Ag+]^2 [SO42-]
1.20 x 10^-5 = (0.0220)^2 [SO42-]
[SO42-] = 0.0248 M
CaSO4 ----------------> Ca+2 + SO42-
Ca+2 0.0248
Ksp = [Ca+2][SO42-]
4.93×10–5 = [Ca+2] (0.0248)
[Ca+2] = 0.00199 M
percentage of Ca+2 = (0.00199 / 0.05 ) x 100
= 3.98 %
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