1. Colligative Properties
Dilution and
Colligative Properties
of Solutions

2. Dilution of Concentrated Solution
moles before dilution = moles after dilution
n = M x V
Mc x Vc = Md x Vd
Mc = molarity of concentrated solution
Vc = volume of concentrated solution
Md = molarity of dilute solution
Vd = volume of dilute solution

4. How many mL of 12 M HCl should be added to water to prepare 400 mL of 0.5 M HCl?
Given : Mc = 12 M Needed: Vc = ?
Md = 0.5 M
Vd = 0.4 L
SOLUTION:
(Mc) (Vc) = (Md) (Vd)
Vc = (Md) (Vd) = (0.5 M) (0.4 L) = L
(Mc) (12 M)

5. COLLIGATIVE PROPERTIES OF SOLUTIONS depend on the molality of the solution
1. Boiling point elevation – the amount by which the boiling point is elevated is determined by the equation:
∆ TB = Kb m
where
∆ TB = boiling point elevation in oC
Kb = molal boiling point constant
(for water = oC/m)
m = molality of the solution

6. What is the boiling point of a solution prepared by dissolving 10 g of NaCl in 25 g of water?
Given: Mole of solute = 10 g/(23+35) = mole
Mass of solvent = kg
Molality = n = mole = 6.88 m x 2
kg kg
Solution:
Solve for the boiling point elevation
∆ TB = Kb m
= (0.512 oC/m) (13.76 m) = 7.05 oC
2. Solve for the final boiling point
TB = 100oC oC = oC

8. 2. Freezing point depression – the amount by which the freezing point is lowered is determined by the equation:
∆ TF = Kf m
where
∆ TF = freezing point depression in oC
Kf = molal freezing point constant
(for water = 1.86 oC/m)
m = molality of the solution

9. What is the freezing point of a solution prepared by dissolving 10 g of NaCl in 25 g of water?
Given: Mole of solute = 10 g/(23+35) = mole
Mass of solvent = kg
Molality = n = mole = 6.88 x 2m
kg kg
Solution:
Solve for the freezing point depression
∆ TF = Kf m
= (1.86 oC/m) (13.76 m) = oC
2. Solve for the final freezing point
TB = 0oC – oC = oC

10. Rock salt melting snow and ice

11. Ethylene glycol raises the boiling point and lowers the freezing point of water

12. 3. Vapor pressure lowering – a nonvolatile solute dissolved in a solvent lowers the equilibrium vapor pressure of the solvent

13. Dead Sea