lecture 3612/5/05. colligative properties physical property based on concentration of solute...
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Lecture 36 12/5/05
Colligative Properties
Physical property
Based on concentration of solute molecules
Doesn’t depend on identity
Colligative Properties
Vapor pressure depression
Boiling point elevation
Freezing point depression
Osmotic pressure
Vapor Pressure depression
Raoult’s LawP = XsolventP°
ΔP = XsoluteP°
Fig. 15-15, p.742
Boiling Point elevation
ΔTb=Kbmi
m = molality = moles solute / kg solvent
What about boiling water for pasta?Kb (water) = 0.512 °C/m
Freezing Point Depression
ΔTf = Kfmi
Salting the sidewalksKf (water) = 1.86 °C/m
ethylene glycol
Coolant Pure Water50/50
C2H6O2/H2O70/30
C2H6O2/H2O
Freezing Point 0°C/32°F -37°C/-35°F -55°C/-67°F
Boiling Point 100°C/212°F 106°C/223°F 113°C/235°F
Osmotic pressure
Π = MRTi
Fig. 15-19, p.749
Reverse Osmosis
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