1. Colligative Properties
Physical properties (melting point and boiling point) of solutions depend on the concentration of solute particles in solution

2. Freezing point depression
When a solute is dissolved in a liquid the freezing point of the solution will be lower ↓ than the pure liquid.
The freezing point of water is less than 0oC if something is dissolved in it.

3. Boiling point Elevation
When a solute is dissolved in a liquid the boiling point of the solution will be higher ↑ than the pure liquid.
The boiling point of water is more than 100oC if something is dissolved in it.

4. 1m electrolyte vs. 1m non-electrolyte
How much ΔT changes depends on
Concentration of SOLUTE PARTICLES in sol’n
1m electrolyte vs. 1m non-electrolyte
1m NaCl vs. 2m NaCl
1m NaCl vs. 2m C12H22O11

5. Which would result in the lowest freezing point / highest boiling point?
1m NaCl (aq)
1m C12H22O11(aq)
1m C2H6O2(aq)
1m CaCl2(aq)

6. Which would result in the lowest freezing point / highest boiling point?
2m NaCl (aq)
1m C12H22O11(aq)
1.5m C2H6O2(aq)
1m CaCl2(aq)

7. Different solvents have different Kf & Kb

8. Formulae ∆Tb = Kb m ∆Tf = Kf m
Delta T = change in freezing point temperature (or boiling point temp)
Kb or Kf is Konstant
molality = mol of solute per Kg of solvent

9. Practice problem I add 25.0g of NaCl to 100.0g of water. BP = 105.65oC
What is the new boiling point?
What is the new freezing point?
BP = oC
FP = -20.3oC

10. Practice problem #2
Benzene has a boiling point of 80.1oC, when 6.2g of an unknown substance is added to 150.0g of benzene, its boiling point increases to 85.2oC. What is the molar mass of the unknown substance?
20.5 g/mol

11. THE END