Question

Ksp of Al(OH)3 is 4.6 x 10^-33

A solution contains 0.20 M Pb2+ and 0.44 M A1+ Calculate the pH range that would allow Al(OH); to precipitate but not Pb(OH)2. The Kop values for Al(OH); and Pb(OH), can be found in this table. minimum pH: maxiumum pH: TOOLS X10

Answer 1

Ksp of Pb(OH)₂ is 1.42*10^-20

and given that Ksp of Al(OH)₃ is 4.6*10^-33

A16H)3 is) Altos y + 3015 Ksp = [A1+?] [ori] 3 4.6x1733 = (0.44) (COM])" Corit? = 10.45 x1o33 (10.45x1027)Y? [on] = = 3.3x10!? M for Al (h), to precipitate, concentration of oth be greater than 3.3x1024 should M. I Pb(OH)2 (5) Pbt2 + 2OH 2) Ksp = [P6] [on] 1.42 xio? 0 = (0-20) [on] ? [on]? = 7.1 X1020 [OH) = 2.66x100 M for of Pb(OH to precipitate, concentration of ort should be greater than 2.6681000M In order to precipitate ALOh, but not Pb(OH2 , range of concentration of ont is following: - the

3-7х1.2 < Сон) 52-64 xtclo - Ang(2-44x10°) 4 -1og [он 1 S - g (1-2xts'', 9. Sя VI Бон < (1:48 ИНt poH = 14 рН= 14 - рон - 11. 48 < "рон VI - 9. SR 14 - (L. 48 < 14 - рон < 14. 9.88 2.52. pH VI S 4.4 2. Minimum pH = 2.52 Maximum PH: 4:42

Thus, the pH range which will allow Al(OH)₃ to precipitate but not Pb(OH)₂ is following:

Minimum pH : 2.52

Maximum pH : 4.42