1. Solution Concentration

2. What is different between the glasses of Kool-aid?

3. Solution concentration can be described generally
Dilute - reduced in strength, weak, watered down.
Concentrated – stronger, pure. Has less water.

4. What is the problem with just using dilute and concentrated as descriptions of the solution concentration?

5. Is solution B dilute or concentrated?
The terms dilute and concentrated are relative.
Scientists need a more precise way of referring to the concentration of a solution.
Concentrated
Dilute
Solution A Solution B Solution C

6. Solution concentration can be described specifically
Do you remember the “mole” from Stoichiometry?
What is a mole?
How might you use it to describe the concentration of a solution?

7. Concentration can be represented by…
Molarity
Molality
Percent by Mass
We will learn about this calculation later on.

8. The ratio of the moles of solute to the volume of solution in liters.
Molarity
The ratio of the moles of solute to the volume of solution in liters.
Moles of solute
Molarity (M) =
Volume in Liters of solution
Used for most chemistry calculations of concentration

9. Molality Molality = moles of solute per kg solvent Moles of solute
kilogram of Solvent
Used for chemistry when volume of solvent is not constant

10. Percent by Mass
Percent by Mass = mass of solute divided by mass of total solution
Mass (g) of solute
% by mass =
Mass of Solvent + Mass of Solute
Used for food, medicine, household cleaners and chemicals

11. How to Calculate Dilutions
Using molarity to calculate dilutions is EASY.
Moles stays the same
Volume changes
Molarity changes
M1V1 = M2V2
Re-arrange to solve for the requested information

12. How to read Molarity 6.0 M NaCl Read: “6 molar solution of NaCl”
Can be abbreviated 6M solution
You must be careful to label the molarity with a capital M so that it is not confused with m for molality.

13. How to make a solution using molarity (6M NaCl)
(a) Add 6 moles NaCl to the volumetric flask. How would you measure that?
6moles NaCl g NaCl
1 mole NaCl
= 351 g NaCl

14. How to make a solution using molarity (6M NaCl)
(b) Add dH2O to dissolve and mix the NaCl
(c) Fill the flask with dH2O until you reach the 1000mL line.

15. Types of Calculations with Molarity:
1. Finding concentration of a solution. 2. Finding the mass of solute needed. 3. Finding the volume of solution made.

16. Finding Concentration
Antifreeze is a solution of ethylene glycol, C2H6O2 in water. If 4.50 L of antifreeze contains 27.5 g of ethylene glycol, what is the concentration of the solution?
27.5 g C2H6O2
1 mol C2H6O2
62.08 g C2H6O2
4.5 L
= mol/L or
M C2H6O2

17. Finding Mass
What mass of sodium carbonate, Na2CO3, is present in 50 ml of a 0.750M solution?
Conversion Factor
50 ml
1 L
0.750 mol
g Na2CO3
1000 mL
1 L
1 mol Na2CO3
= 3.97 g Na2CO3

18. Finding Volume
Conversion Factor
What volume of 1.50 mol/L HCl solution contains 10.0 g of hydrogen chloride?
10.0 g HCl
1 mol HCl
1 L
36.46 g HCl
1.50 mol
= L or 183 mL

19. Practice Problems

20. Practice Problems
1. A L aqueous solution contains 90.0 g of ethanol, C2H5OH. Calculate the molar concentration of the solution in mol·L-1.

21. Practice Problem
2. What mass of NaCl are dissolved in 152 mL of a solution if the concentration of the solution is M?

22. Practice Problem
3. What mass of dextrose, C6H12O6 is dissolved in 325 mL of M solution?

23. Practice Problem
4. A mass of 98 g of sulfuric acid, H2SO4, is dissolved in water to prepare a M solution. What is the volume of the solution?

24. Practice Problem
5. A solution of sodium carbonate, Na2CO3, contains 53.0 g of solute in 215 mL of solution. What is its molarity?

25. Practice Problem
6. What is the molarity of a solution of HNO3 that contains 12.6 g of solute in 5.00 L of solution?