1. 16.2 Concentration of Solutions
Learning Objectives
Solve problems involving the molarity of a solution
Understand dilution and how to do dilution calculations
Define and calculate percent by volume and percent by mass solutions

2. Molarity (M)
Molarity (M) is the most common form of expressing solution concentration
Based on the total solution volume

3. Molarity assumption If someone tells you that you
have a 5.0 M solution you
can assume this:
5 moles solute
1 liter solution

4. Example of Molarity (M) calculation
Calculate the molarity of a solution that contains 5.8g KCl in 550mL of solution.
Solution: 5.8g KCl x 1 mol KCl = mol KCl
74.55g KCl
0.078 mol KCl =
0.55 L solution
Answer: 0.14M

5. Making Dilutions
Most solutions are stored as concentrated stock solutions
Fresh solution made using dilution

6. = Visualizing a Dilution = MiVi MfVf Dilution Moles of solute
Add Solvent
Moles of solute
before dilution (i)
after dilution (f) =
MiVi
MfVf =

7. Dilution Calculation
Stock Solution
How many mL of aqueous 2.00 M MgSO4 solution must be diluted with water to prepare mL of aqueous M MgSO4?
M1= 2.00 M MgSO4
M2 = M MgSO4
V2 = mL of M MgSO4
V1 = ?? mL of 2.00 M MgSO4
M1V1 = M2V2
Solve for V1
V1= M2V2
M 1
V1=(0.400M)(100.0mL) (2.00M)
V1= 20.0 mL (so 20.0 mL of stock solution will be measured and diluted with 80.0 mL of water)
New Solution

8. Percent Solutions

9. Assumptions you can make:
Mass Percent
% = mass solute x 100
mass solution
Assumptions you can make:
A 5.0% solution =
5g solute
100g solution

10. Mass Percent Calculation
What is the mass percent of 500g of water containing 6.50g of copper sulfate?
Solution: CuSO4 x 100% =
(500g +6.50g)
solution
Answer: %

11. Parts per Million (ppm)
Parts per million (ppm) is a ratio of parts of a solute to one million parts of a solution. Usually it is used when describing amount of contaminants in water.
What is the ppm of copper sulfate if you have a solution of 500g of water containing 6.50g of copper sulfate?
Solution: CuSO4 x 106 =12833(12800 ppm)
(500g g)