1. Mixtures

2. Classified by size of solute.
3 Types of Mixtures
Classified by size of solute.

3. 1)Suspension:
Particle size > 1000 nm

4. Examples -
Muddy water
Medicines (shake well)
Paint

5. 2) Colloid:
Particle size between
1 and 1000 nm

6. Examples -
Fog
Blood
Butter
Foam
Smoke

7. 3) Solution:
*Particles size < 1 nm
*Homogeneous

8. Examples-
salt water
sugar water
pure air
alloy (steel)

9. Particles in a suspension settle out.

10. Particles in a colloid scatter light, but aren’t visible to the human eye.

11. Particles in a solution are never visible, and do not scatter light.

12. The Tyndall Effect
Used to distinguish between solutions and colloids.

13. Solutions

14. What determines the RATE of solvation?
Temperature
Agitation
Surface area

15. Aqueous Solutions Water is a “polar” molecule.
The O in the molecule has a partial negative charge.
The H’s have a partial positive charge. d+ d- O H

16. Water solvates (surrounds and stabilizes) the ions.

17. Aqueous Solutions - +
Solvation of anion
Solvation of cation

18. What determines solubility?
Temperature
Pressure (when a gas is involved)
Nature of the particles –
“Like dissolves like”

19. Units of Concentration:
Percent by Mass
% = mass solute x 100
mass solution

20. Example:
What is the percent by mass of NaHCO3 in a solution containing 20g NaHCO3 in 600g H2O?

21. 2. Molarity
M = moles solute
liters solution

22. Example -
What is the molarity of an aqueous solution containing 40.0g of glucose (C6H12O6) in 1.5 L of solution?

23. How many moles of NaOH are in 250mL of a 3.0M NaOH solution?

24. 3. Molality
m = moles solute
kilograms solvent

25. Example -
What is the molality of a solution containing 30.0g of naphthalene (C10H8) dissolved in 500.0g of toluene?

26. How many grams of water would be needed if 100 g sodium chloride was dissolved to make a 1.35 molal solution?

27. 4. Dilution
Allows you to change the concentration of a “stock” solution.
M1V1 = M2V2

28. Example-
What volume, in mL, of 2.00 M calcium chloride stock solution would you use to make L of 0.300M dilute solution?

29. 5. Mole Fraction
XA = molesA
total moles

30. Examples-
What is the mole fraction of NaOH in an aqueous solution that contains 22.8% NaOH by mass?
An aqueous solution of NaCl has a mole fraction of What is the mass of NaCl dissolved in 100.0mL of solution?

31. Colligative Properties
Properties of solutions that are affected by the number of solute particles, but not by their identity.

32. (it doesn’t matter what is dissolved, only how much!)

33. 1. Vapor Pressure Lowering
Vapor pressure is caused by molecules that have evaporated from the surface of a liquid.

34. Why?
When solute is added, particles of solute replace some of the solvent at the surface.
This interferes with the ability of solvent to evaporate, reducing vapor pressure.

35. Also,
In a solution the solvent-solute attraction is usually stronger than the original solvent-solvent attraction, further reducing evaporation.

36. 2. Boiling point elevation
The difference between the normal boiling point of a pure solvent and the boiling point of a solution.

37. ∆Tb = Kb i m

38. Kb H2O =
0.51 °C·Kg/mol

39. example
What is the boiling point of a solution of g of C6H12O6 in 0.75 Kg of H2O?

40. What is the molality of a salt water solution that boils at 106.5°C?

41. 3. Freezing point depression
The difference between the normal freezing point of a pure solvent and the freezing point of a solution.

42. ∆Tf = Kf i m

43. Kf H2O =
-1.86 °C·Kg/mol

44. example
What is the freezing point of water in a solution of g of sucrose (C12H22O11) and 200 g of water?

45. 4. Osmotic Pressure Osmosis – the diffusion of solvent
particles across a semipermeable
membrane from an area of high
solvent concentration to an area of
lower solvent concentration.
Why is this a colligative property?

46. Hypotonic cell Hypertonic cell

47. Π = MRT
The average osmotic pressure of blood is 7.7 atm at 25°C. What concentration of glucose, C6H12O6, will be isotonic with blood?