1. Colligative Properties

2. Definition Properties that depend on the concentration of a solution no matter what the solute’s identity is

4. Boiling Point Elevation A solute lowers the vapor pressure, therefore a solution must be heated to a higher temperature in order to boil ΔT = K B m ΔT – amount of elevation K B – constant for a given solvent m – molality

6. Example A solution consisting of 18.00 g of glucose in 150.0 g of water elevates the boiling point to 100.34ºC. What is the molar mass of glucose?

7. Freezing Point Depression A solute lowers the vapor pressure of the solvent At lower vapor pressure, the rate of melting is higher than the rate of crystallization ΔT = K F m

9. Example What mass of ethylene glycol (C 2 H 6 O 2 ), the main component of antifreeze, must be added to 10.0L of water to produce a solution in the car’s radiator that freezes at –23.3ºC?

10. Example A chemist is trying to identify a human hormone by determining it’s molar mass. A sample weighing.546 g was dissolved in 15.0 g of benzene, and the freezing point depression was determined to be.240ºC. What is it’s molar mass?