1. Chapter 12: Solutions
Mrs. Taylor
HAHS
H. Chem 1B

2. Properties of Solutions
Solution Formation
Solvent
This is the liquid that is doing the dissolving
Solute
This is what is being dissolved
Form a homogenous mixture

3. Saturated vs. Unsaturated Solutions

4. Solubility
Two liquids that dissolve in each other are said to be miscible
Immiscible liquids are insoluble in each other

5. Immiscible vs. Miscible Solutions

6. Factors Affecting Solubility
Solubility increases with the increase in temperature (Easier to dissolve something when the temperature is increased)
Solubility increases with an increase in surface area (ex. CRUSHING)
Few exceptions that occur in the reverse

7. Concentrations of Solutions
Molarity is the concentration of moles per liters
Molarity (M) = moles of solute / liters of solution
Dilute solution contains a low concentration of solute
Concentrated solution contains a high concentration of solute

8. Preparing 1 L of a 1.00 M NaCl Solution
Tro: Chemistry: A Molecular Approach, 2/e

9. Practice Problems:
Calculate the molarity of a solution which contains 0.40 mol of C6H12O6 dissolved in 1.6 L of a solution.
What is the molarity of a solution containing 325 g of NaCl dissolved in 750. mL of solution?(1000 ml = 1L)

10. In complete sentences, describe how you would prepare 500 mL of a 1
In complete sentences, describe how you would prepare 500 mL of a 1.4M solution of sodium chloride

11. Making Dilutions Formula for making a dilution C1 V1 = C2 V2
“Stock solution” is the same as the original solution.

12. Example
A stock solution of HCl has a concentration of 12M. How much of the stock solution would be required to make 325 mL of a 6M solution?

13. Molality
Molality is another way to represent the concentration of a solution.
It is represented by a lower case m.
Molality = moles of solute/kg of solvent
Example: A 4.9m solution of NaCl is dissolved in 1000 grams of water. How many grams of NaCl is this?

14. In your notebook practice:
A solution containing 250 grams of BaCl2 is dissolved in 2000 g of water creating a solution that has a total volume of 2450 mL.
Determine the molarity from the information above.
 Determine the molality from the information above.

15. Solution Stoichiometry
Because molarity relates the moles of solute to the liters of solution, it can be used to convert between amount of reactants and/or products in a chemical reaction
Tro: Chemistry: A Molecular Approach, 2/e

16. Example Problem
What volume of M KCl is required to completely react with L of M Pb(NO3)2?

17. Practice — Solution stoichiometry
43.8 mL of M HCl is needed to neutralize 37.6 mL of Ba(OH)2 solution. What is the molarity of the base?
Tro: Chemistry: A Molecular Approach, 2/e

18. What Happens When a Solute Dissolves?
There are attractive forces between the solute particles holding them together
There are also attractive forces between the solvent molecules
When we mix the solute with the solvent, there are attractive forces between the solute particles and the solvent molecules
If the attractions between solute and solvent are strong enough, the solute will dissolve
Tro: Chemistry: A Molecular Approach, 2/e

19. Table Salt Dissolving in Water
Each ion is attracted to the surrounding water molecules and pulled off and away from the crystal
When it enters the solution, the ion is surrounded by water molecules, insulating it from other ions
The result is a solution with free moving charged particles able to conduct electricity
Tro: Chemistry: A Molecular Approach, 2/e

20. Electrolytes and Nonelectrolytes
Materials that dissolve in water to form a solution that will conduct electricity are called electrolytes
Materials that dissolve in water to form a solution that will not conduct electricity are called nonelectrolytes
Tro: Chemistry: A Molecular Approach, 2/e

21. Molecular View of Electrolytes and Nonelectrolytes
To conduct electricity, a material must have charged particles that are able to flow
Electrolyte solutions all contain ions dissolved in the water
ionic compounds are electrolytes because they dissociate into their ions when they dissolve
Nonelectrolyte solutions contain whole molecules dissolved in the water
generally, molecular compounds do not ionize when they dissolve in water
the notable exception being molecular acids
Tro: Chemistry: A Molecular Approach, 2/e

22. Salt vs. Sugar Dissolved in Water
ionic compounds dissociate into ions when they dissolve
molecular compounds do not dissociate when they dissolve
Tro: Chemistry: A Molecular Approach, 2/e

23. Colligative Properties
Properties that depend on the number of particles dissolved in a given mass of solvent. These properties can change depending on the solute and quantity of it that is dissolved.
EXAMPLES:
Vapor Pressure
Freezing Point Depression
Boiling Point Elevation 23

24. Vapor Pressure of Solutions
The vapor pressure of a solvent above a solution is lower than the vapor pressure of the pure solvent.
The solute particles replace some of the solvent molecules at the surface.
The pure solvent establishes a liquid vapor equilibrium.

25. Vapor Pressure of Solutions
Addition of a nonvolatile solute reduces the rate of vaporization, decreasing the amount of vapor.

26. Other Colligative Properties Related to Vapor Pressure Lowering
Vapor pressure lowering occurs at all temperatures.
This results in the temperature required to boil the solution being higher than the boiling point of the pure solvent.
This also results in the temperature required to freeze the solution being lower than the freezing point of the pure solvent.

27. Boiling-Point Elevation
∆Tb = Kb x m x i
m is the molality
i is the number of ions in solution (covalent: i = 1)
Kb is the molal boiling point elevation constant
It is dependent on the solvent

28. Freezing Point Depression
∆Tf = Kf x m x i
m is the molality
i is the number of ions in solution (covalent: i = 1)
Kf is the molal freezing point constant
It is also dependent on the solvent

29. Colligative Properties of Strong Electrolyte Solutions

30. Kf and Kb

31. Example:
Determine the boiling point and freezing point of a solution in which 600 grams of MgCl2 is dissolved in 2400 grams of water. (Kb = and Kf = 1.86)