Homework
Chapter 13
CHEM 1212K
Spring 2014
1. The solubility of Ar in water at 25°C is 1.6 × 10-3 M when the pressure of the Ar above the
solution is 1.0 atm. Calculaete the solubility of Ar at a pressure of 2.5 atm.
2.
(a) Calculate the mass percentage of NaCl in a solution containing 2.50 g of NaCl in 50.0 g of
water.
(b) A commercial bleaching solution contains 3.85 mass % sodium hypochlorite, NaOCl.
What is the mass of NaOCl in a bottle containing 2.50 kg of bleaching solution?
3. A solution is prepared by dissolving 23.7 g of CaCl2 in 375 g of water. The density of the
resulting solution is 1.05 g/mL. Calculate the molal concentration of CaCl2 in this solution.
4. Calculate (a) the mole fraction (b) malality of urea (MW = 60.0 g/mol) in a solution
prepared by dissolving 16 g of urea in 39g of H2O.
5. A sulfuric acid solution containing 571.6 g H2SO4 per liter of solution has a density of 1.392
g/mL. Calculate (a) the molality, (b) the mole fraction, and (c) the molarity of sulfuric acid in
the solution.
6. The vapor pressure of pure ethanol at 60°C is 0.459 atm. Calculate the vapor pressure, using
Raoult's Law, of a solution prepared by dissolving 10.0 mmol naphthalene (nonvolatile) in
90.0 mmol ethanol.
7. What is the freezing point (°C) of a solution prepared by dissolving 11.3 g of Ca(NO3)2
(formula weight = 164 g/mol) in 115 g of water? The molal freezing point depression
constant for water is 1.86°C/m.
8. A solution is prepared by dissolving 0.60 g of nicotine (a nonelectrolyte) in water to make
12 mL of solution. The osmotic pressure of the solution is 7.55 atm at 25 °C. Calculate the
molecular weight of nicotine.
9. Camphor (C10H16O) melts at 179.8 °C, and it has a particularly large freezing-pointdepression constant, Kf = 40.0 oC/m. When 0.186 g of an organic substance of unknown
molar mass is dissolved in 22.01 g of liquid camphor, the freezing point of the mixture is
found to be 176.7 oC. What is the molar mass of the solute?
10. A sample of 2.05 g of polystyrene of uniform polymer chain length was dissolved in enough
toluene to form 0.100 L of solution. The osmotic pressure of this solution was found to be
1.21 kPa at 25 0C. Calculate the molar mass of the polystyrene.