1. 13.9
Day Five

2. Tro's Introductory Chemistry, Chapter 13
Why Do We Do That?
We spread salt on icy roads and walkways to melt the ice.
We add antifreeze to car radiators to prevent the water from boiling or freezing.
Antifreeze is mainly ethylene glycol.
When we add solutes to water, it changes the freezing point and boiling point of the water.
Tro's Introductory Chemistry, Chapter 13

3. Colligative Properties
The properties of the solution are different from the properties of the solvent
Any property of a solution whose value depends only on the number of dissolved solute particles is called a colligative property.
It does not depend on what the solute particle is.
Tro's Introductory Chemistry, Chapter 13

4. Four Types of Colligative Properties
Boiling Point Elevation
Freezing Point Depression
Vapor Pressure
Osmotic Pressure

5. Boiling Point Elevation

6. Boiling Point Elevation
∆Tb = Kb mi Kb = oC/m What is the b.p. elevation of a solution made from 20.0g of a nonelectrolyte solute and 400 g of water. The molar mass of the solute is 62 grams.

7. Freezing Point Depression
Example: Salt on the roads in the winter!!
∆Tf = Kf mi
Kf = OC/m
A solution consists of 10.3 grams of C6H12O6 dissolved in 250 grams of water. What is the f.p. depression?