properties that depend upon the solute concentration, but n

1
1 M NaCl

• moles NaCl in 1 L?
• moles of particles (ions) in 1 L?

one
two
2
1 M sucrose

• moles sucrose in 1 L?
• moles of particles in 1 L?

one
one
3
Colligative Property

• properties that depend upon the solute
  concentration, but not its identity.

4
Colligative Properties

• vapor pressure
• boiling point
• freezing point
• Osmotic pressure

5
Vapor Pressure Reduction

• a reduction in a solvents vapor pressure from
  the addition of a nonvolatile solute

6
Boiling Point Elevation ?Tb

• the boiling point of the solution minus the
  boiling point of the pure solvent.
• ?Tb Kbmi

7
Problem

• What boiling point elevation occurs if 200 g.
  sucrose (C12H22O11) is added to 500 g. of water?
  Kb for water 0.52 C/m.

0.61 C
8
Freezing Point Depression ?Tf

• the freezing point of the pure solvent minus the
  freezing point of the solution.
• ?Tf Kfmi

9
Problem

• What is the freezing point depression of 0.500 kg
  ethylene glycol (C2H6O2) in 0.500 kg H2O? Kf
  for water1.86C/m.

30 C
10
Osmosis

• a flow of solvent through a semipermeable
  membrane from a less concentrated solution to a
  more concentrated solution.

11
Osmotic Pressure

• the pressure created by the movement of solvent.

12

• The freezing point of water is -0.39C when 39 g.
  of a solute are dissolved in 475 g. of water.
  What is the solutes molar mass?Kf of water
  1.86C /m