Name: __________________________ Period: ______ Date: ____________ Colligative Properties Problems ∆Tb = iKbm Bp= Normal Bp + ∆Tb H2O: Kb = 0.512˚C/m ∆Tf = iKfm Fp= Normal Fp + ∆Tf H2O: Kf = -1.86˚C/m Sucrose = C12H22O11 Glucose = C6H12O6 1. What colligative properties are displayed by each of the following situations? a. Antifreeze is added to a car’s cooling system to prevent freezing when the air temperature is below 0 ºC. b. freezing point depression Ice melts on a sidewalk after salt has been spread on the sidewalk. Freezing point depression 2. If two solutions of equal amounts in a U-tube are separated by a semipermeable membrane, will the level of the more concentrated solution or the less concentrated solution rise? The level of the more concentrated solution will rise because the side with less concentration has more solvent than the other side, and the solvent will want to move across the membrane to reach equilibrium. The solute also doesn't move because the membrane is semipermeable and the solute is too big to go through. Since solvent is going into the more concentrated side and nothing is leaving that side, it's level will rise. 3. What is the freezing point depression of a 1.5 m solution of sucrose (a nonelectrolyte) in water? =1*-1.86*1.5= -2.79 0+-2.79= -2.79c 4. What is the freezing point depression of water in a solution of 17.1 grams sucrose C 12H22O11 and 100. gram water? (molar mass of sucrose = 342.34g/mol) Hint: find molality first a. What is the new freezing point of the solution? 5. If the freezing point of an aqueous solution of glucose is found to be –0.325C, what is the molality of the solution? 6. What is the expected freezing point of a solution containing 95.0 gram of glucose dissolved in 500. gram of water? (hint: find freezing point depression, then new freezing point) 7. Given 1.50 m solutions of each of the following electrolytic substances, what is the expected change in the freezing point of the solvent? a. KI Name: __________________________ Period: ______ Date: ____________ b. MgSO4 8. Determine the molality of an unknown nonelectrolyte in water, with a freezing point depression of -0.940ºC 9. Calculate the freezing point and boiling point of a solution of 40. grams of NaCl dissolved in 400. g of water. 10. Determine the molality of an aqueous solution of a nonelectrolyte in water with a boiling point of 102.8C 11. What is the expected boiling point elevation for a solution that contains 150 g of NaCl in 800. grams water? 12. The boiling point elevation for an aqueous solution of water and barium nitrate Ba(NO3)2 is 2.65 C. Determine the molality of the solution.
