1. Lecture 3612/5/05

2. Colligative Properties Physical property Based on concentration of solute molecules Doesn’t depend on identity

3. Colligative Properties Vapor pressure depression Boiling point elevation Freezing point depression Osmotic pressure

4. Vapor Pressure depression Raoult’s Law P = X solvent P° ΔP = X solute P°

5. Fig. 15-15, p.742

6. Boiling Point elevation ΔT b =K b mi m = molality = moles solute / kg solvent

7. What about boiling water for pasta? K b (water) = 0.512 °C/m

8. Freezing Point Depression ΔT f = K f mi

9. Salting the sidewalks K f (water) = 1.86 °C/m

10. ethylene glycol CoolantPure Water 50/50 C 2 H 6 O 2 /H 2 O 70/30 C 2 H 6 O 2 /H 2 O Freezing Point0°C/32°F-37°C/-35°F-55°C/-67°F Boiling Point100°C/212°F106°C/223°F113°C/235°F

11. Osmotic pressure Π = MRTi

12. Fig. 15-19, p.749

13. Reverse Osmosis