COLLIGATIVE PROPERTIES

COLLIGATIVE PROPERTIES OF SOLUTIONS

1.    Colligative Properties depend on the concentration of solute in solvent and not upon the identity of the solute.

a.    Vapor pressure reduction is a colligative property in which the pressure of the vapor over a solvent is reduced when a nonvolatile solute dissolved in the solvent.  It is directly proportional to the concentration of a solution.

b.    Boiling Point Elevation is a colligative property in which the boiling point of a solvent is raised when a nonvolatile solute is dissolved in the solvent.  It is directly proportional to the concentration of a solution.

c.    Freezing point depression is a colligative property in which the freezing point of a solvent is lowered by the addition of a solute.

d.    Osmotic pressure is the force that makes osmosis possible.

2.    The gas pressure resulting from the vapor molecules over the liquid is the vapor pressure.

3.    Boiling Point is the temperature at which the vapor pressure of a liquid becomes equal to the atmospheric pressure.

4.    Osmosis refers to the movement of solvent through a semi permeable membrane from a region of higher concentration to a region of lower concentration.

5.    The most commonly used measurements of concentration are molarity, molality and mole fraction.

Boiling Point elevation	Freezing Point Depression
Tb= Kbm Where: Tb= boiling point elevation (oC)           Kb= molal boiling point elevation constant   of solvent (oC/m) m= molality (m)	Tf= Kfm Where: Tf= freezing point depression (oC) Kb= molal boiling point elevation constant of solvent (oC/m) m= molality (m)

Vapor pressure Reduction	Osmotic pressure
Pa= XaPoa Where: Pa= vapor pressure lowering of solution Xa=  mole fraction of solute Poa=  vapor pressure of pure solvent Units of pressure: mmHg, atm, Pa, torr,	π=MRT Where:   ¶=  osmotic pressure in atm                M=        Molarity (mol/L)                R= 0.0821 L atm/mol K                T=  temperature in Kelvin         K=  oC + 273