Outline Chapter 11 Crystals,
Ions, and Solutions
11-1. Ionic and Covalent Crystals
11-2. The Metallic Bond
11-3. Molecular Crystals
11-4. Solubility
11-5. Polar and Nonpolar Liquids
11-6. Ions in Solution
11-7. Evidence for Dissociation
11-8. Water
11-9. Water Pollution
11-10. Acids
11-11. Strong and Weak Acids 1112. Bases
11-13. The pH Scale
11-14. Salts
1
11-1. Ionic and Covalent
Crystals
Most solids are crystalline, meaning
the particles that compose them are
arranged in repeated patterns.
Amorphous solids have particles
irregularly arranged. Crystalline
solids fall into four classes:
1. Ionic
2. Covalent
Amorphous
Glass
3. Metallic
4. Molecular
2
Table 11.1
3
11-1. Ionic and Covalent
Crystals
Ionic crystals are formed by
the attraction between
positive and negative ions.
1. Face-centered cubic
ionic crystals have ions
located at the corners and
centers of the faces of a
series of cubes.
2. Body-centered cubic
ionic crystals have each ion
located at the center of a
cube at whose corners are
ions of the other kind.
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11-1. Ionic and Covalent
Crystals
Covalent crystals are formed
when pairs of electrons are
shared between adjacent
atoms. Some crystals are
neither wholly ionic nor
wholly covalent but contain
bonds of mixed character.
5
Dr. Tacy Hall’s Artificial Diamond Presses
Pictures to the left
and below are of
diamonds made
from graphite. Dr.
Hall made
diamonds from
peanut butter as
well.
6
11-2. The Metallic Bond
The metallic bond is formed by a "gas" of
electrons that moves freely through the assembly
of metal ions that form a solid metal. The metallic
bond accounts for the characteristics of metals.
M
M
M
M
M
M
M
M
M
M
M
M
M
M
e-
M
M-
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
eM
ee-M
e
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Fig. 11.10
The Electron Sea is
responsible for the shiny
surfaces of metals.
8
11-3. Molecular Crystals
Some liquids and solids
are formed through the
action of van der Waals
forces, named after the
Dutch physicist Johannes
van der Waals.
Polar-polar interaction occurs
between polar molecules
whose positively and negatively
charged ends cause them to
line up with the ends that have
opposite charges adjacent.
9
Fig. 11.11
The water molecules in a snowflake are held
together by van der Waals bonds. Ice is less
dense than its liquid and thus floats.
10
Fig. 11.15
Cling film
owes its
properties
to polar
molecules
on its
surface.
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11-3. Molecular Crystals
Non-polar-non-polar interaction occurs between
non-polar molecules when the molecule's electrons
at any given moment are distributed unevenly. This
creates temporarily charged molecules whose
adjacent ends having opposite signs results in an
attractive force.
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11-3. Molecular Crystals
Examples of these
weak temperary
interactions is
nitrogen gas.
Nitrogen gas is
normally non-polar
but if the temperature
is low enough, these
non-polar molecules
can form a liquid,
liquid nitrogen.
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11-4. Solubility
In a solution, the substance present in larger
amount is the solvent; the other is the solute. The
concentration of a solution is the amount of solute
in a given amount of solvent. The solubility of a
substance is the maximum amount that can be
dissolved in a given quantity of a particular solvent
at a given temperature. Examples of solutions:
liquid in liquidsolid in liquidgas in liquidgas in gassolid in solid-
alcoholic drinks
salt water
sodas
air
metal alloy
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11-4. Solubility
A saturated solution contains the maximum amount
of solute possible at a given temperature; a
supersaturated solution contains more dissolved
solute than is normally possible at a given
temperature and is usually unstable.
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Supersaturated and Supercooled
http://www.youtube.com/watch?v=HnSg2cl09PI
http://axiomsun.com/home/video/supercooled_water.html
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11-4. Solubility
The solubilities of solids increase with increasing
temperatures, while the solubilities of gases in
liquids decrease with increasing temperatures. The
boiling point of a solution is usually higher than that of
the pure solvent, and its freezing point is lower.
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11-4. Solubility
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11-5. Polar Liquids
A polar liquid is a
substance whose molecules
behave as if negatively
charged at one end and
positively charged at the
other. The molecules of a
nonpolar liquid have
uniform charge distributions.
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11-5. Polar Liquids
Polar liquids dissolve
only ionic and polar
covalent compounds.
Nonpolar liquids
dissolve only nonpolar
covalent compounds.
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Intermolecular Forces
Dipole-Dipole Forces
-
OδHδ+
+
Solid
+
OδHδ+
Hδ+
Liquid
Hδ+
OδHδ+
Hδ+
Gas
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11-5. Polar Liquids
Soaps and
Detergents have
polar head and a
non-polar tail. The
tail is attracted to
the non-polar
greasy dirt and the
polar head is
attracted to the
polar water
molecules.
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11-5. Polar Liquids
Dissociation
refers to the
separation of a
compound into
ions when it
dissolves.
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11-5. Polar Liquids
Electrolytes are
substances that
dissociate into ions
when dissolved in
water;
nonelectrolytes are
soluble covalent
compounds that do
not dissociate in
solution. Electrolytes
in solution are able to
conduct electric
current.
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11-6. Ions in Solution
Ions in solution have
their own sets of
properties that differ
from their original
atoms and from the
original solute.
Dissociation is a type of
chemical change. The
properties of a solution
of an electrolyte are the
sum of the properties of
the ions present in the
solution.
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11-7. Evidence of Dissociation
In 1887, the Swedish chemist
Svante Arrhenius proposed that
many substances exist as ions in
solution. His hypothesis was based
on two points:
1. Reactions between electrolytes
in solution occur almost
instantaneously, but very slowly or
not at all if the electrolytes are dry.
2. Electrolyte solutions have lower
freezing points than comparable
solutions of nonelectrolytes.
Svante
Arrhenius
(1859-1927)
26
Fig. 11.31
This device
used the color
difference
between
chromic and
dichromate
ions to
measure the
alcohol
concentration
in a person’s
breath.
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11-8. Water
Seawater has an average salt content, or salinity, of
3.5 percent.. "Hard" water is freshwater that
contains Ca2+ and Mg2+ ions in solution; "soft" water
is free of Ca2+ and Mg2+ ions.
Hard water left
a deposit of
scale in this
pipe.
These household
water softeners are
ion-exchange resins.
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11-8. Water
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11-9. Water Pollution
Sources of water pollution
include:
1. Industrial pollutants
2. Agricultural fertilizers and
pesticides
3. Thermal pollution
The biochemical oxygen
demand, or BOD, is the amount
of oxygen needed to completely
oxidize the organic material in a
sample of water.
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11-9. Water Pollution
A municipal waste water treatment plant.
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Fig. 11.37
Water pollution from a
steel mill. Public anger
has forced governments
to act against such abuse
of the environment.
Below fertilizers caused
algae raft.
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11-10. Acids
An acid is a hydrogen-containing substance that
increases the number of H+ ions present when the
substance is dissolved in water. The H+ ions released
when an acid dissociates in water combine with water
molecules to produce hydronium ions, H3O+.
The water solutions of
acids taste sour, and
acids change the color of
litmus dye from blue to
red.
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11-11. Strong Acids and Weak
Acids
Strong acids dissociate completely; weak
acids dissociate only slightly. Some
substances, such as carbon dioxide, do not
contain hydrogen but produce acidic
solutions by reacting with water to liberate H+
ions from water molecules.
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11-12. Bases
A base is a substance that contains hydroxide
groups and whose solution in water increases
the number of OH- ions present. Strong bases
dissociate completely; weak bases dissociate
only slightly. The water solutions of bases have
a bitter taste, a soapy feel, and turn red litmus
to blue.The name alkali is sometimes used for
a substance that dissolves in water to give a
basic solution. The terms alkaline and basic
mean the same.
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11-13. The pH Scale
The pH scale expresses the exact
degree of acidity or basicity of a solution
in terms of its H+ ion concentration. A
solution that is neither acidic nor basic is
said to be neutral and has a pH of 7.
Acidic solutions have pH values of less
than 7. Basic solutions have pH values of
more than 7.
36
Finding the [H+] from the pH.
To find the [H+] from the pH just insert the pH into 10-pH.
For example, if the pH is 4 the [H+]
is 10-4.
If the pH is 6 the [H+] is 10-6
If the pH is 10 the [H+] is 10-10
If the pH is 8 the [H+] is 10-8
To find the pH from the [H+] just insert the [H+] into -log [H+].
For example, if the [H+] is 10-4 the pH is 4
If the [H+] is 10-9 the pH is 9
If the [H+] is 10-2 the pH is 2
37
Calculating pH and [H+]
pH = - log [H+]
[H+] = antilog (-pH) = 10-pH
If [H+] = 2.0 x 10-9 then
pH = -log(2.0 x 10-9) = 8.69897
pH =8.70 [H+] = 10-8.7
If pH = 3.2 then
[H+] = antilog(-3.2) = 6.31 x 10-4
pH Meter
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Fill in the Blanks
pH
[H+]
2.5
0.0032
______
8.2
6.3x10
______-9
5.6
_____
2.8x10-6
2.6
_____
2.6x10-3
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11-14. Salts
When a basic solution is mixed with an acidic
solution, the base destroys, or neutralizes, the
properties of the acid and vice versa. The process is
called neutralization. In neutralization reactions,
H+ and OH- ions join to form water molecules. Ions
left in solution as a result of neutralization can
combine to form a salt when the solution is
evaporated to dryness. Most salts are crystalline
solids that consist of positive metal ions and
negative nonmetal ions.
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Lecture Quiz 11
1. What are the 4 types of crystalline
solids? What type is diamond?
2. What is an electrolyte?
3. What happens when you cool a
saturated solution?
4. What ions are primarily responsible
for hard water?
5. What is the pH of a solution
containing 3.7 x 10-5 M HCl?
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42
Lecture Quiz 11
1. What are the 4 types of crystalline
solids? Ionic, Covalent, Metallic, Molecular
What type is diamond? Covalent
2. What is an electrolyte? Produces ions.
3. What happens when you cool a
saturated solution?Solid forms on bottom.
4. What ions are primarily responsible
for hard water? Ca2+and/or Mg2+
5. What is the pH of a solution
containing 3.7 x 10-5 M HCl? 4.4
43
Lecture Quiz 11
1. Is water polar or non-polar?
2. What are 3 types of solutions?
3. What is meant by saturation?
4. What ions are primarily responsible
for hard water?
5. What is BOD?
6. What is the pH of water?
44
Lecture Quiz 11
1. Is water polar or non-polar?
2. What are 3 types of solutions?
Solid in liquid, gas in liquid, liquid in liquid, gas in gas, solid in
solid, etc.
3. What is meant by saturation?
You cannot dissolve anymore solute in the solvent.
4. What ions are primarily responsible
for hard water? Ca and Mg
5. What is BOD? Biological Oxygen Demand
6. What is the pH of water? 7
2+
2+
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