1. Solutions and Colloids
Chapter 9
Solutions and Colloids

2. Solution or Colloid Group these? Marshmallows Wine Air Clouds Smoke
Automobile oil
Milk of magnesia

3. Colloids and Solutions
What is the difference in appearance? (Can be observed)

4. Characteristics of Solutions
Appearance
Distribution of Particles
Separation of Components
Variable Compositions Can Be Made

5. Colloids particle diameter is between 1nm and 1000 nm
Colloid particles have very large surface areas, which accounts for these two characteristics of colloidal systems
they scatter light and, therefore, appear turbid, cloudy, or milky
they form stable dispersions; that is, they do not settle out

6. Types of Solutions
Solvent:
Solute:

7. Types of Colloids

8. Colloids
Tyndall effect: a characteristic of colloids in which light passing through the colloid scatters
examples of colloids that exhibit the Tyndall effect are smoke, serum, and fog

9. Properties of Mixtures

10. Colloids and Solutions
What is the cause of the differences? (What do we think is going on?)
Video Link Changing a colloidal suspension into a solution with acid.

11. Definitions Solubility:
those compounds with low solubility are said to be insoluble,
those compounds with higher solubility are said to be soluble

12. More Definitions saturated solution: unsaturated solution:
supersaturated solution:
Link to Video

13. Soluble or Insoluble
Explain why some substances are soluble and other substances are not soluble by giving one example of each. Used balanced equations in you discussion.
You may use the solubility rules page 161

14. Solvation
What happens when substances dissolve? What forces are involved? Use water as a solvent for specific examples.
Ionic?
Covalent?

15. Water as a Solvent
How water dissolves ionic compounds
water is a
ions

16. Water as a Solvent How water dissolves molecular compounds
nonpolar covalent molecules
polar covalent molecules dissolve because
Each individual molecule is

17. Electrolytes Video Link-electrolytes and non-electrolytes
Video Link – Weak and strong electrolytes

18. Electrolytes cations migrate to the negative electrode (the cathode)
anions migrate to the positive electrode (the anode)
the movement of ions constitutes an electric current
electrolyte:
nonelectrolyte
strong electrolyte:
weak electrolyte:

19. Stoichiometry
How can we count particles in a solution?

20. Percent Composition Percent composition:
weight of solute per volume of solution (w/v);
a solution of 10 g of table sugar in 100 mL of solution, for example, has a concentration of 10 percent w/v
weight of solute per weight of solution (w/w);
essentially the same as w/v except that the weight of the solution is used instead of its volume
volume of solute per volume of solution (v/v);
example, a solution of 40 mL of ethanol in 100 mL of aqueous solution is 40 percent v/v

21. Molarity Molarity: moles of solute per liter of solution
example: tell how to prepare 2.0 L of 0.15 M NaOH
first we find the number of moles of NaOH required
next convert 0.30 mol NaOH to g NaOH

22. 4.5

23. Solution Stoichiometry
The concentration of a solution is the amount of solute present in a given quantity of solvent or solution.
M = molarity =
moles of solute
liters of solution
What mass of KI is required to make 500. mL of
a 2.80 M KI solution?
M KI
M KI
volume KI
moles KI
grams KI
4.5

24. Molarity
problem: the concentration of NaCl in blood serum is approximately 0.14 M. What volume of serum contains 2.0 g of NaCl?
first find the number of moles NaCl in 2.0 g NaCl
next find the volume in liters that contains this many moles of NaCl

25. Molarity
If we dilute a solution, the number of moles of solute remains the same; use this relationship:
M1V1 = M2V2
problem: how do you prepare 200 mL of 3.5 M aqueous solution of acetic acid if you have a bottle of 6.0 M acetic acid
first find the number of L of 6.0 M acetic acid needed

26. Dilution is the procedure for preparing a less concentrated solution from a more concentrated solution.
Dilution
Add Solvent
Moles of solute
before dilution (i)
after dilution (f) =
MiVi
MfVf =
4.5

27. How would you prepare 60.0 mL of 0.200 M
HNO3 from a stock solution of 4.00 M HNO3?
MiVi = MfVf
4.5

28. Colligative Properties
Colligative property: any property of a solution that depends on the number of solute particles, and not on the nature of the particles
We study two colligative properties
freezing-point depression
osmosis

29. Freezing-Point Depression
One mole of any particle dissolved in 1000 grams of water lowers the freezing point of water by 1.86°C
the nature of the particles does not matter, only the number of particles
Depression of freezing point has a number of practical applications
we use NaCl and CaCl2 to melt snow and ice
we use ethylene glycol as antifreeze in automobile radiators

30. Freezing-Point Depression
Problem: if we add 275 g of ethylene glycol, C2H6O2, per 1000 g of water in a car radiator, what will be the freezing point of the solution?
ethylene glycol is a molecular compound; it dissolves in water without dissociation
first find the number of moles of ethylene glycol
each mole lowers the freezing point by 1.86°C
the freezing point of the solution will be

31. Freezing-Point Depression
Problem: what will be the freezing point of a solution prepared by dissolving one mole of K2SO4 in 1000 grams of water?
K2SO4 is an ionic solid and dissociates to ions when dissolved in water
one mole of K2SO4 gives three moles of ions
the freezing point is lowered by

32. Osmosis

33. Osmosis
semipermeable membrane: a membrane with tiny pores that are big enough to allow solvent molecules to pass through them, but not big enough to allow the passage of large solute molecules
osmosis: the movement of solvent particles through a semipermeable membrane from a region of lower solute concentration (higher solvent concentration) to a region of higher solute concentration (lower solvent concentration)
osmotic pressure: the pressure necessary to prevent osmosis
osmolarity (osmol): the molarity multiplied by the number of particles produced by each formula unit of solute

34. Osmosis Isotonic solutions: solutions with the same osmolarity
isotonic solution: a term used primarily in the health sciences to refer to a solution with the same osmolarity as blood plasma and red blood cells
hypotonic solution: a solution with lower osmolarity than blood plasma and red blood cells
hemolysis: the swelling and bursting of red blood cells because they cannot resist the increase in osmotic pressure when put into a hypotonic solution
hypertonic solution: a solution with higher osmolarity than red blood cells

35. Osmosis
Problem: an 0.89 percent w/v NaCl solution is referred to as physiological saline solution. What is the osmolarity (osmol) of this solution?
0.89 w/v NaCl = 8.9 g in 1 L of solution
first we calculate the number of moles of NaCl in this solution
because each mole of NaCl dissolved in water dissociates into two ions, the osmolarity of the solution is