1.   Calculate solubility for PbI₂ in g/L (K_sp = 8.7x10^-9)                      (10)
2.   Calculate molar solubility for PbSO₄ in 0.50 M Na₂SO₄          (10)
3.   Calculate K_sp if 0.062 g Ca₃(PO₄)₂soluble in 1.00 L of H₂O        (10)
4.   Calculate K_sp  for M(OH)₃ if saturated solution gives pH of 9.00   (10)
5.   Calculate pH range for separating 1.0M Mg⁺² from 1.0M Zn⁺². (10)
6.   If 50.0mL 0.020M Ca⁺² mixed with 50.0mL 0.030M CrO₄^-2,  (10)
     will precipitate form?   Explain with calculation!
7.  4.00 M Na₃PO₄ solution has density of 1.20 g/mL.                    (12 )
    Calculate:  (a) weight % Na₃PO₄      (b) molality     (c) mole fraction Na₃PO₄
8.   The vapor pressure of pure water is exactly 600 torr.                 (10)
      Solution consisting of 108 g H₂O and 54.0 g of nonvolatile solute displays
      vapor pressure of 500 torr. Calculate FW of solute.
9.  Solution prepared using 33.3 g CaCl₂ and exactly 400 g H₂O.       (10)
      Determine boiling & freezing points of this solution.
10. Determine F.P. if 3.00m CaBr₂ solution ionizes 80.0%.              (10)

Answers
1.  PbI₂  Pb⁺²  +  2 I^-1         K = 8.7x10^-9 = [Pb⁺²][I^-1]² =(x)(2x)² = 4x³
       x            x          2x            x = 0.0013
                                              (0.0013 mol/L)(461 g/mol) = 0.60 g PbI₂

2.   PbSO₄ Pb⁺²  +  SO₄^-2          Ksp = 6.3x10^-7 = [Pb⁺²][SO₄^-2] = (x)(x+0.50) @ 0.50x
           x             x         x+0.50          x = 1.3x10^-6 M

3.   Solubilty Ca₃(PO₄)₂ = (0.062g/L)/(310 g/mol) = 2.0x10^-4 M
      Ca₃(PO₄)₂ 3 Ca⁺²     +    2 PO₄^-3
      2.0x10^-4 M         6.0x10^-4 M     4.0x10^-4 M         K_sp = [Ca⁺²]³[PO₄^-3]² = [6.0x10^-4]³[4.0x10^-4]² =3.5x10^-17

4.  When pH=9.00,  [OH^-1] = 1.0x10^-5
     M(OH)₃ M⁺³    +    3 OH^-1
                       3.3x10^-6 M    1.0x10^-5 M                      Ksp = [M⁺³][OH^-1]³ =  [3.3x10^-6][1.0x10^-5]³ = 3.3x10^-21

5.   Mg(OH)_2(s)  Mg⁺²    +   2  OH^{-1
                           1.0M                      x M}
     Mg(OH)₂:    Ksp = 7.1x10^-12 = [Mg⁺²][OH^-1]²
                                   7.1x10^-12 = [1.0][OH^-1]²
                                   [OH^-1] = 2.7x10^-6 M     pOH = 5.58    pH =8.42   pH range equal or less than 8.42

6.  After mixing:  [Ca⁺²] = 0.010M        [CrO₄^-2] = 0.015M         Ksp for CaCrO₄ = 7.1x10^-4
     Ion Product = [Ca⁺²] [CrO₄^-2] = [0.010] [0.015] = 1.5x10^-4
     Since IP < Ksp, NO PPT forms!

7.   Assume 1.00 L or 1200 g total mass
      contains 4.00 mol Na₃PO₄ or 656 g Na₃PO₄   and  544g H₂O (1200 - 656)
     (a)  % Na₃PO₄ = (656/1200)x100 = 54.7
     (b)  m = 4.00mol/0.544kg = 7.35
     (c)  mol H₂O = 544/18 = 30.2       mol fraction Na₃PO₄ = 4.00/34.2 = 0.117

8.      P_sol  =  P_w X_w
       500 torr = (600 torr)X_w     X_w = 0.833         n_w = 108/18 = 6.00      n_s = 54.0/FW

       X_w = n_w/(n_w + n_s) = 6.00/(6.00 + 54.0/FW) = 0.833        FW =  45.0 g/mol

9.   mol CaCl₂ = 33.3/111 = 0.300          m = 0.300/0.400kg = 0.750
     DT_b = imK_b = 3(0.750)(0.512) = 1.15     BP = 101.2°C
     DT_f = imK_f  = 3(0.750)(-1.86) = -4.19    FP = -4.2° C

10.  Assume 100 particle CaBr₂      CaBr₂ Ca⁺²   +   2Br^-1
                                                                   20              80                160   =  260       i = 260/100 = 2.60

      DT_f= imK_f = (2.60)(3.00)(1.86) = 14.5   F.P. = normal F.P. -  DT_f = -14.5°C