Solutions
SOLUTE + SOLVENT
SOLUTION
State of Matter
Gas:
homogenous mixture of gases (Air…)
Liquid:
solvent: liquid
solute: gas
solid
(soda water: CO2/H2O; brine: NaCl/H2O)
solvent: liquid
solute: liquid
(ethanol in water)
Solid:
solvent: solid
(gold-silver alloy)
solute: solid
solvent: solid
(Dental-filling alloy)
solute: liquid
Terms to Know…
Dissolve: solute + solvent  solution.
Crystallization: solution  solute + solvent.
Saturation: crystallization and dissolution are in
equilibrium.
Solubility: amount of solute required to form a saturated
solution.
Supersaturated: a solution formed when more solute is
dissolved than in a saturated solution.
Miscible: two liquids that mix.
Immiscible: two liquids that do not mix.
Like Dissolves Like
“Rule”: polar solvents dissolve
polar solutes. Non-polar solvents
dissolve non-polar solutes. Why?
+ – + –
– + – +
+ – + –
NaCl
If ΔHsoln is too endothermic a
solution will not form.
NaCl in octane (C8H18): the ionLondon forces are weak because
octane is non-polar. Therefore,
the ion-London forces do not
compensate for the separation of
ions.
NaCl dissolves nicely in water.
octane
water
Terminology:
Solubility:
is the maximum amount of the solute that will
dissolve in a definite amount of solvent (at a given t°)
g/100 mL
Concentration: ratio of the solute and the solvent
Dilute solutions
Concentrated solutions
Saturated solutions:
solutepure
solute dissolved
Supersaturated solutions:
g/100 mL
KNO3
PbCl2
NaCl
Solubility curves
t°
Temperature Effects: Solids
• Experience tells us that sugar
dissolves better in warm
water than cold.
• As temperature increases,
solubility of solids generally
increases.
• Sometimes, solubility
decreases as temperature
increases (e.g. Ce2(SO4)3).
Properties of Water

Most abundant liquid

Vital to life

Universal solvent
1. High melting and boiling points
M.p.:
0.0°C
B.p.: 100.0°C
(0.1 MPa)
Hydrogen Bonding
Special
150
H2
O
100
Group 4
Group 5
Boiling Point (deg C)
case of
dipole-dipole forces.
By experiments:
boiling points of
compounds with H-F,
H-O, and H-N bonds
are abnormally high.
Intermolecular
forces are
abnormally strong.
50
Group 6
Group 7
0
H2S
e
H2
S
-50
-100
SnH
4
GaH
SiH
-150
H2T
e
4
4
CH
-200
4
0
1
2
3
Period
4
5
Water Molecule
Solutions
Phase Diagram of H2O
The
melting point curve
slopes to the left because
ice is less dense than
water.
Triple point occurs at
0.0098°C and 4.58 mmHg.
Normal melting
(freezing) point is 0°C.
Normal boiling point is
100°C.
Critical point is 374°C
and 218 atm.
2. Density
0.0°C (ice)
0.0°C (liquid)
3.98°C
25.0°C
3. Surface tension:
0.91680 g/cm3
0.99984 g/cm3
0.99997 g/cm3
0.99704 g/cm3
high
Bottom of meniscus
4. High heat of vaporization
40.70 kJ/mol
5. High heat of fusion
6.02 kJ/mol
6. High specific heat
75.20 kJ/mol
1. Chemically pure water
2. Water of crystallization or hydration
CuSO4 5H2O(s)
D
CuSO4(s) + 5H2O(g)
(CaSO4)2 H2O
(plaster of paris)
CaSO4 2H2O
(gypsum)
Na2CO3 10H2O
3. Groundwater
Cations
Anions
Ca2+
HCO3-, CO32-
Na+
OH-
Mg2+
SO42-
K+
Cl-
Fe2+, Fe3+
NO3-
NH4+
F-, PO43-
Hard water


Soft water
Temporary hard water
HCO3- (bicarbonate)
Permanent hard water
Water
Softening


Boiling
Softening agents


Distillation
Ion-exchange
Mineral water
Thermal water
precipitation
complex formation