1 Colligative Properties of Nonelectrolyte Solutions Colligative properties are properties that...
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1 ative Properties of Nonelectrolyte Sol Colligative properties are properties that depend only on the number of solute particles in solution and not on the nature of the solute particles. Vapor-Pressure Lowering P 1 = X 1 P 1 0 Boiling-Point Elevation DT b = K b m Freezing-Point Depression DT f = K f m Osmotic Pressure (p) p = MRT
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Glycerin (C 3 H 8 O 3 ) is a nonvolatile nonelectrolyte with a density of 1.26 g/mL at 25˚C. Calculate the vapor pressure at 25˚C of a solution made by adding 50.0mL of glycerin to 500.0mL of water. The vapor pressure of pure water at 25˚C is 23.8 torr. P 1 = X 1 P 1 0 Vapor-Pressure Lowering P 1 = new vapor pressure of solution X 1 = mole fraction of solvent P 1 = vapor pressure of pure solvent 0 P water/glycerin solution = X water P pure water mL glycerin x 1.26 g x mol = mol glycerin mL 92.11g mL H 2 O x 1g x mol = mol H 2 O mL 18.02g X H2O = moL H 2 O = mol mol P water/glycerin soln = (23.8 torr) P solution = 23.3 torr
Transcript of 1 Colligative Properties of Nonelectrolyte Solutions Colligative properties are properties that...
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Colligative Properties of Nonelectrolyte Solutions
Colligative properties are properties that depend only on the number of solute particles in solution and not on the nature of the solute particles.
Vapor-Pressure Lowering P1 = X1 P 10
Boiling-Point Elevation DTb = Kb m
Freezing-Point Depression DTf = Kf m
Osmotic Pressure (p) p = MRT
Lowering Vapor Pressure
Vapor pressure – pressure exerted by the vapor over the solution
Nonvolatile – no vapor pressure
P1 = X1 P 10Vapor-Pressure Lowering
(Raoult’s Law)
Glycerin (C3H8O3) is a nonvolatile nonelectrolyte with a density of 1.26 g/mL at 25˚C. Calculate the vapor pressure at 25˚C of a solution made by adding 50.0mL of glycerin to 500.0mL of water. The vapor pressure of pure water at 25˚C is 23.8 torr.
P1 = X1 P 10Vapor-Pressure Lowering
P1 = new vapor pressure of solution X1 = mole fraction of solvent P1 = vapor pressure of pure solvent
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Pwater/glycerin solution = Xwater P pure water0
50.0 mL glycerin x 1.26 g x mol = 0.680 mol glycerin mL 92.11g500.0 mL H2O x 1g x mol = 27.75 mol H2O mL 18.02g
XH2O = 27.75 moL H2O = 0.9800 27.75 mol + 0.680 mol
Pwater/glycerin soln = 0.9800 (23.8 torr) Psolution = 23.3 torr
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PA = XA P A0
PB = XB P B0
PT = PA + PB
PT = XA P A0 + XB P B
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Ideal Solution
When both the solute and solvent are volatile (have measureable vapor pressures) …
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PT is greater thanpredicted by Raoults’s law
PT is less thanpredicted by Raoults’s law
ForceA-B
ForceA-A
ForceB-B< & Force
A-BForceA-A
ForceB-B> &
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Osmotic Pressure (p)Osmosis is the selective passage of solvent molecules through a porous membrane from a dilute solution to a more concentrated one.
A semipermeable membrane allows the passage of solvent molecules but blocks the passage of solute molecules.Osmotic pressure (p) is the pressure required to stop osmosis.
dilute moreconcentrated
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HighP
LowP
Osmotic Pressure (p)
p = iMRT
M is the molarity of the solutionR is the gas constantT is the temperature (in K)
solvent solution
time
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A cell in an:
isotonicsolution
hypotonicsolution
hypertonicsolution
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Chemistry In Action: Reverse Osmosis
