1. Molarity (M):
State the ratio between the number of moles of solute & the volume of solution (in liters).
Molarity (M) =

2. Example:
Find the molarity of 500 mL of a solution which contain 60 g of NaOH dissolved in water.
Solute=
60 g NaOH
÷ 40 g/mol
= 1.5 mol
Solution=
500 mL
= 0.5 L
Molarity (M) = = =
3.0 mol/L
or 3.0 molar

3. Preparing Molar Solutions:
How could you prepare 1 L of a 1.5 M of magnesium chloride solution?
M =
moles of solute =
molarity x liters of solution
= 1.5 mol/L x 1 L
= 1.5 mol MgCl2
mass of MgCl2 =
= 1.5 mol x 95 g/mol
= g
Must be dissolved in water
up to 1 L of solution.
(Use a volumetric flask)

4. Dilution:
Dilution is adding extra solvent to decrease the concentration of a solution
The amount of solute stays the same, but the concentration decreases
Dilution Formula:
M1 x V1 = M2 x V2

5. Example – What Volume of 12. 0 M KCl is needed to prepare 5. 00 L of 1
Example – What Volume of 12.0 M KCl is needed to prepare 5.00 L of 1.50 M KCl Solution?
Initial Solution (1) Final Solution (2)
Concentration 12.0 M M
Volume ? L L
M1 x V1 = M2 x V2
Rearrange and Apply Equation:

6. Making a Solution by Dilution
Dilute L of 12.0 M solution
to 5.00 L

7. Diluting Solutions:
Find the volume of 2.00 M NaOH stock solution needed to make 0.5 L of 0.3 M sodium hydroxide solution.
V1= ?
M1 = 2.00 M
V2= 0.5 L
M2 = 0.3 M
M1V1 = M2V2
V1=
V1=
V1=
0.075 L
or 75 mL

8. Molality (m):
State the ratio between the number of moles of solute & the mass of solvent (in kg).
Molality (m) =

9. Example:
Find the molality of a solution made by adding 4.5 g of NaCl to 100 g of water.
Solute=
4.5 g NaCl
÷ 58.5 g/mol
= mol
Solvent=
100 g
= 0.1 kg
Molality (m) = = =
0.77 mol/kg
or 0.77 mol.kg-1