1. Physical Properties of Solutions
Chapter 12
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2. A solution is a homogenous mixture of 2 or more substances
The solute is(are) the substance(s) present in the smaller amount(s)
The solvent is the substance present in the larger amount

3. A saturated solution contains the maximum amount of a solute that will dissolve in a given solvent at a specific temperature.
An unsaturated solution contains less solute than the solvent has the capacity to dissolve at a specific temperature.
A supersaturated solution contains more solute than is present in a saturated solution at a specific temperature.
Sodium acetate crystals rapidly form when a seed crystal is
added to a supersaturated solution of sodium acetate.

4. Molecular view of the formation of solution
Three types of interactions in the solution process:
solvent-solvent interaction
solute-solute interaction
solvent-solute interaction
Molecular view of the formation of solution
DHsoln = DH1 + DH2 + DH3

5. “like dissolves like”
Two substances with similar intermolecular forces are likely to be soluble in each other.
non-polar molecules are soluble in non-polar solvents
CCl4 in C6H6
polar molecules are soluble in polar solvents
C2H5OH in H2O
ionic compounds are more soluble in polar solvents
NaCl in H2O or NH3 (l)

7. Which one of the following would be immiscible with water?

8. In which of the following solvents would you expect KBr to be most soluble?
A) C6H14 (hexane) D) CCl4 (carbon tetrachloride)
B) CH3CH2OH (ethanol) E) C6H12 (cyclohexane)
C) C6H6 (benzene)

9. Concentration Units
The concentration of a solution is the amount of solute present in a given quantity of solvent or solution.
Percent by Mass
x 100%
mass of solute
mass of solute + mass of solvent
% by mass = =
x 100%
mass of solute
mass of solution

10. 1. Calculate the percent by mass of potassium nitrate in a solution made from 45.0 g KNO3 and 295 mL of water. The density of water is g/mL.
2. A solutions is prepared by dissolving 23.7 g of CaCl2 in 375 g of water. The density of the resulting solution is 1.05 g/ml . The concentration of CaCl2 is __________ by % mass.

11. Review: mass, mole, molar mass relationship
Mole Fraction (X)
XA =
moles of A
sum of moles of all components
Review: mass, mole, molar mass relationship

12. Molecular mass (or molecular weight) is the sum of
the atomic masses (in amu) in a molecule.
SO2 1S
32.07 amu 2O
+ 2 x amu
SO2
64.07 amu
For any molecule
molecular mass (amu) = molar mass (grams)
1 molecule SO2 = amu
1 mole SO2 = g SO2

13. Molar mass or molecular mass = mass in grams / mole
mole = mass/molar mass
Mass in grams = moles x molar mass
3. Find the mole fraction of the components of the solutions described in practice problems #1.
4. The mole fraction of He in a gaseous solution prepared from 4.0 g of He, 6.5 g of Ar, and 10.0 g of Ne is __________.

14. Concentration Units Continued
Molarity (M)
M =
moles of solute
liters of solution
Molality (m)
m =
moles of solute
mass of solvent (kg)

15. What is the molality of a 5
What is the molality of a 5.86 M ethanol (C2H5OH) solution whose density is g/mL?
m =
moles of solute
mass of solvent (kg)
M =
moles of solute
liters of solution
Assume 1 L of solution:
5.86 moles ethanol = 270 g ethanol
927 g of solution (1000 mL x g/mL)
mass of solvent = mass of solution – mass of solute
= 927 g – 270 g = 657 g = kg
m =
moles of solute
mass of solvent (kg) =
5.86 moles C2H5OH
0.657 kg solvent
= 8.92 m

16. 4. How many grams of water are needed to dissolve 27
4. How many grams of water are needed to dissolve 27.8 g of ammonium nitrate NH4NO3 in order to prepare a m solution?
5. What is the mass percent CH3OH of a m CH3OH(aq) solution.
6. Calculate the molality of a 15.0% by mass solution of MgCl2 in H2O. The density of this solution is g/mL.
7. The concentration (M) of HCl in a solution prepared by dissolving 5.5 g of HCl in 200 g of is __________ M. The density of the solution is 0.79 g/mL.

17. Temperature and Solubility
Solid solubility and temperature
solubility increases with increasing temperature
solubility decreases with increasing temperature

19. Fractional crystallization is the separation of a mixture of substances into pure components on the basis of their differing solubilities.
Suppose you have 90 g KNO3 contaminated with 10 g NaCl.
Fractional crystallization:
Dissolve sample in 100 mL of water at 600C
Cool solution to 00C
All NaCl will stay in solution (s = 34.2g/100g)
78 g of PURE KNO3 will precipitate (s = 12 g/100g). 90 g – 12 g = 78 g

20. Temperature and Solubility
O2 gas solubility and temperature
solubility usually decreases with increasing temperature

21. Pressure and Solubility of Gases
The solubility of a gas in a liquid is proportional to the pressure of the gas over the solution (Henry’s law).
c is the concentration (M) of the dissolved gas
c = kP
P is the pressure of the gas over the solution
k is a constant for each gas (mol/L•atm) that depends only on temperature
low P
high P
low c
high c

22. 8. The solubility of nitrogen gas at 25°C and a nitrogen pressure of 522 mmHg is 4.7 x 10–4 mol/L. What is the value of the Henry's Law constant in mol/L·atm? (ans: 6.8 x 10–4 mol/L·atm)
Note: 1 atm = 760 mmHg

23. Colligative Properties of Nonelectrolyte Solutions
Colligative properties are properties that depend only on the number of solute particles in solution and not on the nature of the solute particles.
Vapor-Pressure Lowering
P1 = X1 P 1
P 1
= vapor pressure of pure solvent
X1 = mole fraction of the solvent
Raoult’s law
If the solution contains only one solute:
X1 = 1 – X2
P 1
- P1 = DP = X2
X2 = mole fraction of the solute

24. Fractional Distillation Apparatus

25. 9. The vapor pressure of pure water at 25 °C is 23. 8 torr
9.The vapor pressure of pure water at 25 °C is 23.8 torr. What is the vapor pressure (torr) of water above a solution prepared by dissolving 18.0 g of glucose (a nonelectrolyte, MW = g/mol) in 95.0 g of water? (21 torr)
10. The vapor pressure of pure ethanol at 60 °C is atm. Raoult's Law predicts that a solution prepared by dissolving 10.0 mmol naphthalene (nonvolatile) in 90.0 mmol ethanol will have a vapor pressure of __________ atm. ( 0.413)

26. Boiling-Point Elevation
DTb = Tb – T b
T b is the boiling point of
the pure solvent
T b is the boiling point of
the solution
Tb > T b
DTb > 0
DTb = Kb m
m is the molality of the solution
Kb is the molal boiling-point
elevation constant (0C/m)
for a given solvent

27. Freezing-Point Depression
DTf = T f – Tf
T f is the freezing point of
the pure solvent
T f is the freezing point of
the solution
T f > Tf
DTf > 0
DTf = Kf m
m is the molality of the solution
Kf is the molal freezing-point
depression constant (0C/m)
for a given solvent

29. DTf = Kf m Kf water = 1.86 oC/m DTf = Kf m
What is the freezing point of a solution containing 478 g of ethylene glycol (antifreeze) in 3202 g of water? The molar mass of ethylene glycol is g.
DTf = Kf m
Kf water = 1.86 oC/m =
3.202 kg solvent
478 g x
1 mol
62.01 g
m =
moles of solute
mass of solvent (kg)
= 2.41 m
DTf = Kf m
= 1.86 oC/m x 2.41 m = 4.48 oC
DTf = T f – Tf
Tf = T f – DTf
= 0.00 oC – 4.48 oC = oC

30. 11. The freezing point of ethanol is -114. 6 °C
11. The freezing point of ethanol is °C. The molal freezing point depression constant
for ethanol is 2.00 °C/m. What is the freezing point (°C) of a solution prepared by dissolving 50.0 g of glycerin a nonelectrolyte) in 200 g of ethanol? ( C)
12. George is making spaghetti for dinner. He places 4.01 kg of water in a pan and brings it to a boil. Before adding the pasta, he adds 58 g of table salt to the water and again brings it to a boil. The temperature of the salty, boiling water is __________°C. It is a nice day at sea level so that pressure is 1.00 atm. Assume negligible evaporation of water. Kb for water is 0.52°C/m.

31. Determining Molar mass by freezing point or boiling point
13. When 24.0 g of glucose (a nonelectrolyte) are dissolved in 500. g of water, the solution has a freezing point of –0.47°C. What is the molar mass of glucose? Kf of water is 1.86°C/m. (190 g/mol)
14. When 12.1 g of the sugar sucrose (a nonelectrolyte) are dissolved in exactly 800 g of water, the solution has a freezing point of –0.082°C. What is the molar mass of sucrose? Kf of water is 1.86°C/m.

32. Osmotic Pressure (p)
Osmosis is the selective passage of solvent molecules through a porous membrane from a dilute solution to a more concentrated one.
A semipermeable membrane allows the passage of solvent molecules but blocks the passage of solute molecules.
Osmotic pressure (p) is the pressure required to stop osmosis.
more
concentrated
dilute

33. Osmotic Pressure (p) p = MRT High P Low P
time
solvent
solution
High P
Low P
p = MRT
M is the molarity of the solution
R is the gas constant
T is the temperature (in K)

34. A cell in an:
isotonic
solution
hypotonic
solution
hypertonic
solution

35. Colligative Properties of Nonelectrolyte Solutions
Colligative properties are properties that depend only on the number of solute particles in solution and not on the nature of the solute particles.
Vapor-Pressure Lowering
P1 = X1 P 1
Boiling-Point Elevation
DTb = Kb m
Freezing-Point Depression
DTf = Kf m
Osmotic Pressure (p)
p = MRT

36. Colligative Properties of Electrolyte Solutions
0.1 m NaCl solution
0.1 m Na+ ions & 0.1 m Cl- ions
Colligative properties are properties that depend only on the number of solute particles in solution and not on the nature of the solute particles.
0.1 m NaCl solution
0.2 m ions in solution
van’t Hoff factor (i) =
actual number of particles in soln after dissociation
number of formula units initially dissolved in soln
i should be
nonelectrolytes 1
NaCl 2
CaCl2 3

37. Colligative Properties of Electrolyte Solutions
Boiling-Point Elevation
DTb = i Kb m
Freezing-Point Depression
DTf = i Kf m
Osmotic Pressure (p)
p = iMRT

38. A colloid is a dispersion of particles of one substance throughout a dispersing medium of another substance.
Colloid versus solution
collodial particles are much larger than solute molecules
collodial suspension is not as homogeneous as a solution
colloids exhibit the Tyndall effect

40. Hydrophilic and Hydrophobic Colloids
Hydrophilic: water-loving
Hydrophobic: water-fearing
Stabilization of a hydrophobic colloid

41. The Cleansing Action of Soap

42. Chemistry In Action:
Desalination

43. Chemistry In Action:
Reverse Osmosis