Colligative Properties of Solutions. Step 1 Breaking up the solute into individual components (expanding the solute) Step 2 Overcoming the intermolecular forces in the solvent to make room for the solute (expanding the solvent) Step 3
DeltaHhyd combines deltaH2 and delta H3
Example: For NaCl
deltaHsoln = 786 kJ/mol – 783 kJ/mol
= 3 kJ/mol
we must supply a small amount of energy
Why does it happen so readily?
Processes run to disorder (ping pong demo)
Lake had thermal layers
With excess CO2 on bottom.
August 21, 1986 A cloud of gas
Boiled from Lake Nyos, killing
2000 people and many animals.
It was CO2 !
BUT, not always. . .Temperature and Solubility
Psoln = XsolventPosolvent
P vapor pressure of solution
X mole fraction of solvent
Po vapor pressure of pure solventVapor Pressure
OSMOTIC PRESSURESo, what is a colligative property anyway?
Used to determine the molar masses of substancesWhy Should We Care?
Change in vapor pressure, boiling point elevation, or freezing point depression or osmotic pressure
Moles of solute
where c is the molarity of the solution
Colloids are suspensions of particles that have a size between approximately 10 Å and 2,000Å dispersed in another medium.