Solutions

Solubility Problems
sol. 1
1.  Determine the solubility of sodium chloride at 60oC.
2.  Determine the solubility of KNO3 at 20oC in 40 grams of water.
3.  Determine the solubility of potassium chloride at 70oC in 65 g of water.
Answers:
sol2

Molality
Molality = moles of solute/Kg of solvent                    m = mol
                                                                                           Kg
Solve:
molality

Freezing Point Depression and Boiling Point Elevation Problems
sol3
1.  425 g of C 6 H12O6 was dissolved in 875 g of water.  What is the boiling point of the solution?
2.  18.0 g of a nonelectrolyte was dissolved in 2.00 x 102 g of water.  Its freezing point is -2.79oC.  What is the molecular mass of the nonelectrolyte?
Answers:
sol4

Equilibrium Constant
Keq  =  [Products]
             [Reactants]

"Coefficients are Exponents"
equil1
equil2

Solubility Product Constant
1.  Calculate the solubility constant, Ksp for copper II sulfide, if the [CuS] = 2.51 x 10-18 M
2.  Calculate the solubility of  barium carbonate if the Ksp for barium carbonate = 1.2 x 10-8
3.  Calculate the molarity of the calcium ion & hydroxide ion if the Ksp for Ca(OH)2 = 5.5 x 10-6
Answers:
ksp1
        Ksp = [Cu+2][S-2]
             = [2.51 x 10-18][2.51 x 10-18]
             = 6.30 x 10-36

ksp2
        Ksp = [Ba+2][SO4-2]
      1.2 x 10-8 = [x][x]
      x2 = 1.2 x 10-8
      x   = 1.1 x 10-4

ksp3
       Ksp = [Ca+2][OH-1]2
       5.5 x 10-6 = [x][2x]2
       4x3 = 5.5 x 10-6
         x  = 1.1 x 10-2
       [Ca+2] = 1.1 x 10-2   [OH-] = 2.2 x 10-2