Molarity (M)
• Expresses solution concentration
• M = moles of solute / liters of solvent
• Molarity, molar, M, and mol/liter all
represent the same ratio
Episode 1003
• Ex #1 A saline solution contains 0.90 g
per 95 mL of solution. What is the
molarity?
• M = moles of solute / liters of solution
0.90 g NaCl 1 mol NaCl
= 0.015 mol NaCl
58.5 g NaCl
95 mL
1 Liter
1000 mL
= 0.0950 L
0.015 mol NaCl
0.0950 L
0.16 M
Episode 1003
• Ex #2 How many moles of solute are
contained in 2.5 L of 0.30 M CaCl2?
• M = moles of solute / liters of solution
0.30 M = 0.30 moles/1 liter
2.5 L
0.30 mol
1L
= 0.75 mol
If grams are
involved, convert to
grams to moles or
moles to grams.
Episode 1003
Colligative Properties
• Any of the properties of a solution that
change when the concentration of the
solution changes.
• Depend on the number of particles
dissolved in a given mass of solvent
Episode 1003
Examples of Colligative
Properties
• Vapor Pressure Depression
– The lowering of the vapor pressure of a
liquid that occurs when a substances are
dissolved in the liquid
• Vapor pressure:
– The pressure of a vapor in equilibrium with
its liquid
Episode 1003
• Freezing Point Depression
– The lowering of the freezing point of a liquid
that occurs when substances are dissolved in
the liquid
• (Ex. Using antifreeze in car radiators and salt on
icy roads)
• Boiling Point Elevation
– The raising of the boiling point of a liquid that
occurs when substances are dissolved in the
liquid
• (Ex. Antifreeze in a car acts as a coolant in the
summer.)
Episode 1003