iii. colligative properties (p.552)
DESCRIPTION
Ch. 15 - Solutions. III. Colligative Properties (p.552). A. Definitio`n. Colligative Property property that depends on the concentration of solute particles, not their identity. B. Types. Freezing Point Depression ( t f ) f.p. of a solution is lower than f.p. of the pure solvent - PowerPoint PPT PresentationTRANSCRIPT
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II
III
I III. Colligative Properties
(p.552)
III. Colligative Properties
(p.552)
Ch. 15 - SolutionsCh. 15 - Solutions
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A. Definitio`nA. Definitio`n
Colligative PropertyColligative Property
• property that depends on the
concentration of solute particles, not
their identity
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B. TypesB. Types
Freezing Point DepressionFreezing Point Depression (tf)
• f.p. of a solution is lower than f.p. of the pure solvent
Boiling Point ElevationBoiling Point Elevation (tb)
• b.p. of a solution is higher than b.p. of the pure solvent
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B. TypesB. Types
View Flash animation.
Freezing Point Depression
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B. TypesB. Types
Solute particles weaken IMF in the solvent.
Boiling Point Elevation
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B. TypesB. Types
Applications• salting icy roads• making ice cream• antifreeze
• cars (-64°C to 136°C)• fish & insects
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C. CalculationsC. Calculations
t: change in temperature (°C)
k: constant based on the solvent (°C·kg/mol)
m: molality (m)
i: # of particles
t = k · m · i
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C. CalculationsC. Calculations
i i -# of Particles-# of Particles
• Nonelectrolytes (covalent)• remain intact when dissolved • 1 particle
• Electrolytes (ionic)• dissociate into ions when dissolved• 2 or more particles
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C. CalculationsC. Calculations
At what temperature will a solution that is composed of 0.73 moles of glucose in 225 g of water boil?
m = 3.2mi = 1tb = kb · m · i
WORK:
m = 0.73mol ÷ 0.225kg
GIVEN:b.p. = ?tb = ?
kb = .512°C·kg/moltb = (.512°C·kg/mol)(3.2m)(1)
tb = 1.64°C
b.p. = 100°C + 1.64°C
b.p. = 101.64°C
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C. CalculationsC. Calculations
Find the freezing point of a saturated solution of NaCl containing 28 g NaCl in 100. mL water.
m = 4.8m
i = 2
tf = kf · m · i
WORK:
m = 0.48mol ÷ 0.100kg
GIVEN:
f.p. = ?
tf = ?
kf = 1.86°C·kg/mol
tf = (1.86°C·kg/mol)(4.8m)(2)
tf = 18°C
f.p. = 0.00°C - 18°C
f.p. = -18°C