Factors Affecting Solubility
1. temperature
2. particle size
3. mixing
As To , rate
As size
, rate
More mixing, rate
4. nature of solvent/solute (“like dissolves like”, polar dissolves polar)
Measuring
Concentration
Concentration…a measure of solute-to-solvent ratio
concentrated
“lots of solute”
vs.
dilute
“not much solute”
“watery”
Add water to dilute a solution; boil water off to concentrate it.
Measuring Concentration
“The amount of solute in a solution”
A. Parts per million (ppm)  also, ppb
and ppt
= g solute/1,000,000 g solution
– commonly used for minerals or
contaminants in water supplies
B. Molarity (M) = moles of solute
L of solution
– used most often
C. Molality (m) = moles of solute
kg of solvent
mol
M
L
One mole, in solution.
Molarity
molarity (M) 
moles of solute
L of solution
0.25m 
0.25 mol
1L
liter of solution
Molarity
 Find
the molarity of a solution containing
75 g of MgCl2 in 250 ml of water.
75 g MgCl2
1 mol MgCl2
95.21 g MgCl2 0.25 L water
M 
mol
L
= 3.2M MgCl2
Molality
molality (m) 
moles of solute
kg of solvent
0.25m 
0.25 mol
1 kg
mass of solvent only
1 kg water = 1 L water
Molality
 Find
the molality of a solution containing
75 g of MgCl2 in 250 ml of water.
75 g MgCl2
1 mol MgCl2
95.21 g MgCl2 0.25 kg water
m 
mol
kg
= 3.2m MgCl2
Molality
 How
many grams of NaCl are req’d to
make a 1.54m solution using 0.500 kg of
water?
0.500 kg water 1.54 mol NaCl 58.44 g NaCl
1 kg water
1.5m 
1.5 mol
1 kg
1 mol NaCl
= 45.0 g NaCl
Factors Affecting Solubility
1. temperature
2. particle size
3. mixing
As To , rate
As size
, rate
More mixing, rate
4. nature of solvent/solute (“like dissolves like”, polar dissolves polar)
Solubility (“Dissolution”)
• Temperature
-The solubility of most
solids in water
increases as the
temperature of the
sol’n increases.
-The solubility of gases
in water decreases with
increasing temperature
Solubility (“Dissolution”)
Experiment 1:
Add 1 drop of red food coloring
Before
AFTER
Miscible – “mixable”
two gases or two liquids
that mix evenly
Water
Water
Water
Water
COLD
HOT
COLD
HOT
B
A
B
A
Solubility (“Dissolution”)
Experiment 2:
Add oil to water and shake
AFTER
Before
Immiscible – “does not mix”
two liquids or two gases
that DO NOT MIX
Oil
Water
Water
T0 sec T30 sec
Gas Solubility
CH4
2.0
Solubility
O2
CO
1.0
He
0
10
20
30
Temperature (oC)
40
50
Solubility: forming a “saturated”
solution in equilibrium
UNSATURATED
SOLUTION
more solute
dissolves
SATURATED
SOLUTION
no more solute
dissolves
SUPERSATURATED
SOLUTION
becomes unstable,
crystals form
increasing concentration
“Oil and Water Don’t Mix”
• Oil is nonpolar
• Water is polar
“Like dissolves like”,
nonpolar dissolves
nonpolar, nonpolar
does not dissolve
polar
Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 470
Water Molecule
Water is a POLAR molecule
d+
H2O
d-
d+
H+
H+
O2-
d-
Dissolving of NaCl in Water
Na+
ions
Water molecules
Clions
NaCl(s) + H2O  Na+(aq) + Cl-(aq)
Ethanol is Polar
dH
d+
O
H
Polar bond
H
C
H
Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 469
C
H
H
Ethanol and Water are Soluble
H
H
H
H
C
O
O
H
C H
‘Like dissolves like’
H
Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 469
H
Cleaning Action
of Soap
Micelle
Timberlake, Chemistry 7th Edition, page 573
emulsifying agent (emulsifier):
-- molecules w/both a polar AND a nonpolar end
-- allows polar and nonpolar substances to mix
e.g., soap
detergent
lecithin
MODEL OF A SOAP MOLECULE
Na1+
POLAR
HEAD
NONPOLAR
HYDROCARBON
TAIL
eggs
Interstitial Spaces
Oil
Oil
Oil
Oil
Oil
Oil
Oil
Non-polar
"immiscible"
Layer
dissolved
solid
Water
Water
Water
Water
Water
Water
Water
Water
Polar
red food
coloring
Clogged Pipes – Hard Water
Step 1: Acid rain is formed
H2O + CO2
H2CO3
carbonic acid
Step 2: Acid rain dissolves limestone
H2CO3 + CaCO3
Ca(HCO3)2
H2CO3 + MgCO3
Mg(HCO3)2
‘hard’ water
Water softner
Pipes develop Scales
Step 3: Hard water is heated and deposits scales
Ca(HCO3)2
D
CaCO3(s) + H2O + CO2
scales on pipes
Mg(HCO3)2
D
MgCO3(s) + H2O + CO2
Water Purification
Anion
Cation
Exchanger
Hard
Water
H+
OH-
H+
(b)
Fe3+
OH-
Deionized
Water
OH-
H+
(a)
Ca2+
H+
Mg2+
Na+
Exchanger
H+
OH-
H+
OH-
(c)
OH-
H+
OH-
H+
OH-
Hard water is softened by exchanging Na+ for Ca2+, Mg2+, and Fe3+.
Corwin, Introductory Chemistry 2005, page 361
(a)
(b)
(c)
The cations in hard water are exchanged for H+.
The anions in hard water are exchanged for OH-.
The H+ and OH- combine to give H2O.
Pure water does not conduct an
electric current
Source of
electric power
Pure
water
Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 215
Ionic Solutions conduct a Current
Source of
electric power
Free ions
present
in water
Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 215
electrolytes: solutes that dissociate in solution
-- conduct electric current because of free-moving ions
e.g., acids, bases, most ionic compounds
-- are crucial for many cellular processes
-- obtained in a healthy diet
-- For sustained exercise or a bout of the flu, sports drinks
ensure adequate electrolytes.
nonelectrolytes: solutes that DO NOT dissociate
-- DO NOT conduct electric current (not enough ions)
e.g., any type of sugar
Strong electrolytes exhibit nearly 100% dissociation.
NOT in water:
in aq. solution:
NaCl
1000
1
Na1+
0
999
+
Cl1–
0
999
Weak electrolytes exhibit little dissociation.
CH3COOH
NOT in water:
in aq. solution:
1000
980
CH3COO1–
0
20
+
H1+
0
20
“Strong” or “weak” is a property of the substance.
We can’t change one into the other.
Electrolytes
Electrolytes - solutions that carry an electric current
strong electrolyte
NaCl(aq)
Na+ + Cl-
Timberlake, Chemistry 7th Edition, page 290
weak electrolyte
HF(aq)
H+ + F-
nonelectrolyte
Colligative Properties  depend on concentration of a solution
Compared to solvent’s…
a solution w/that solvent has a…
…normal freezing point (NFP)
…lower FP
…normal boiling point (NBP)
…higher BP
FREEZING PT.
DEPRESSION
BOILING PT.
ELEVATION
Applications (NOTE: Data are fictitious.)
1. salting roads in winter
FP
water
0oC
(NFP)
water + a little salt
–11oC
water + more salt
–18oC
BP
100oC
(NBP)
103oC
105oC
2. antifreeze (AF) /coolant
FP
water
0oC
(NFP)
BP
100oC
(NBP)
water + a little AF
–10oC
110oC
50% water + 50% AF
–35oC
130oC
Effect of Pressure on Boiling Point
Boiling Point of Water at Various Locations
Feet
Boiling
Location
above Patm (kPa)
Point
sea level
(C)
Top of Mt. Everest, Tibet
29,028
32
70
Top of Mt. Denali, Alaska
20,320
45.3
79
Top of Mt. Whitney, California
14,494
57.3
85
Leadville, Colorado
10,150
68
89
Top of Mt. Washington, N.H.
6,293
78.6
93
Boulder, Colorado
5,430
81.3
94
Madison, Wisconsin
900
97.3
99
New York City, New York
10
101.3
100
-282
102.6
100.3
Death Valley, California