gaya antar molekul dan cairan dan padatan
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Gaya Antarmolekul dan
Cairan dan PadatanChapter 11
Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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Suatu fasa (phase) adalah bagian homogen dari
suatu sistem yang berkontak dengan bagian
sistem yang lain namun terpisah dengan batas
yang jelas. 2 Fasa
Fasa padat - es
Fasa cair - air
11.1
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11.2
Intermolecular forcesare attractive forces between molecules
Intramolecular forceshold atoms together in a molecule.
(covalent bond)
Intermolecular vs Intramolecular
41 kJ to vaporize 1 mole of water (inter) 930 kJ to break all O-H bonds in 1 mole of water (intra)
Generally,
intermolecularforces are much
weaker than
intramolecular
forces.(only about
15% as strong)
Measure of intermolecular force
boiling point
melting point
DHvap
DHfus
DHsub
Teori kinetik molekul cairan dan padatan
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Types of Intermolecular Forces (IMF)
Should actually be called Interparticulate Forces
(molecules, ions, and/or atoms) Ion - ion fo rces
Ion -dipole forces
Dipole-dipole forces
Dispers ion Forces
Hydrogen Bond s
Ion - ion forces: (latt ice energy -ion ic compound)
Remember Chapter 9
Force depends on the charge on the ions andthe distance separating the ions
(STRONG FORCES)
E = kQ+Q-
r
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Intermolecular Forces
1. Ion-Dipole Forces
Attractive forces between an ionand a polar molecule
Example: ions in solution
11.2
Ion-Di
pole Interaction
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11.2
The strength of the interaction depends on the charge and
size of the ion and on the magnitude of the dipole moment
and size of the molecule.
Higher charge, smaller sizestrong interaction
Water molecules
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Intermolecular Forces
2. Dipole-Dipole Forces (permanent dipole moment)
Attractive forces between polar molecules
Orientation of Polar Molecules in a Solid
11.2
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Intermolecular Forces
3. Temporary dipoles (Dispersion forces)
What attractive force occurs in nonpolar substances?Attractive forces that arise as a result of temporary
dipoles inducedin atoms or molecules
11.2
ion-induced dipole interaction
dipole-induced dipole interaction
Ion induced
Dipole induced
Instantaneous dipole
The electron distribution of atom is distortedby the force exerted by the ions or polar
molecules.
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Polarizabil i tyis the ease with which the electron distribution
in the atom or molecule can be distorted.
Polarizability increases with:
greater number of electrons
more diffuse electron cloud
The likelihood of a dipole moment being induced depends not only
on the charge of the ion or the strength of the dipole but also on
the polarizabilityof the atom or molecules.
Melting point increases as
the number of electrons inthe molecule increase.
Dispersion forcesusually increase with
molar mass (more
electrons), or size of
the atom.
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Induced dipoles interacting with each other. This type ofinteraction produces dispersion forces, which arise as a result of
temporary dipoles induced in atoms or molecules, is
responsible for the condensation of nonpolar gases.
**Dispersion force exists between all species.
Polarizability allows gases containing atoms or nonpolar
molecules (e.g.He,N2) to condense.
At any instant it is likely that the atom has a dipole moment
created by a specific positions of electrons. This dipole
moment is called instantaneous dipole.
London Dispers ion Force (Dispers ion force)
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S
What type(s) of intermolecular forces exist between
each of the following molecules?
HBrHBr is a polar molecule: dipole-dipole forces. There are
also dispersion forces between HBr molecules.
CH4
CH4is nonpolar: dispersion forces.
SO2SO2is a polar molecule: dipole-dipole forces. There are
also dispersion forces between SO2molecules.
11.2
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Intermolecular Forces
4. Hydrogen Bond
11.2
Thehydrogen bond
is a special dipole-dipole interactionbetween the hydrogen atom in a polar N-H, O-H, or F-H bond
and an electronegative O, N, or F atom.
A HB A HAor
A & B are N, O, or F
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Hydrogen Bonds:
Strength of H bonds: up to 40 kJ/mol
Lots of H bonds = strong compare with strength of typical covalent bonds:
250 kJ/mole)
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Why is the hydrogen bond considered a
special dipole-dipole interaction?
Decreasing molar mass
Decreasing boiling point
11.2
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Properties of Liquids
Surface tens ionis the amount of energy required to stretch
or increase the surface of a liquid by a unit area.
Strong
intermolecularforces
High
surface
tension
11.3
The intermolecular attraction tend
to pull molecules into liquids and
cause the surface to tighten like a
plastic film.
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Properties of Liquids
Viscosityis a measure of a fluids resistance to flow.
11.3
Strong
intermolecular
forces
High
viscosityCH2-OH
CH-OH
CH2-OH
Gliserolviskositasnya jauh lebih besar
daripada semua cairan pada tabel di atas
S lid t l t t
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A crys tall ine so l idpossesses rigid and long-range order. In a
crystalline solid, atoms, molecules or ions occupy specific
(predictable) positions. (e.g. NaCl)
An amorphoussol iddoes not possess a well-defined
arrangement and long-range molecular order. (e.g. glass)
A un it cel lis the basic repeating structural unit of a crystalline
solid.
Unit Cell
lattice
point
Unit cells in 3 dimensions 11.4
At lattice points:
Atoms,
Molecules,
or Ions
Solid---crystal structure
Structures of crystalline solids:
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Figure 11.15
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11.4
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Shared by 8
unit cells
Shared by 2
unit cells
11.4
Shared by 4
unit cells
Corner atom edge atom face centered
atom
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11.4Jml atom = 1 Jml atom = 2 Jml atom = 4
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When silver crystallizes, it forms face-centered cubic
cells. The unit cell edge length is 409 pm. Calculate
the density of silver.
d=mV
V= a3= (409 pm)3= 6.83 x 10-23cm3
4 atoms/unit cell in a face-centered cubic cell
m= 4 Ag atoms107.9 g
mole Agx
1 mole Ag
6.022 x 1023atomsx = 7.17 x 10-22g
d=mV
7.17 x 10-22g
6.83 x 10-23cm3= = 10.5 g/cm3
11.4
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Types of Crystals
Ionic Crystals
Lattice points occupied by cations and anions
Held together by electrostatic attraction
Hard, brittle, high melting point
Poor conductor of heat and electricity
CsCl ZnS CaF2
11.6
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Types of Crystals
Covalent Crystals
Lattice points occupied by atoms
Held together by covalent bonds
Hard, high melting point
Poor conductor of heat and electricity
11.6diamond graphite
carbon
atoms
allotrope
sp3
sp2
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Types of Crystals
Molecular Crystals
Lattice points occupied by molecules
Held together by intermolecular forces
Soft, low melting point
Poor conductor of heat and electricity
11.6
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Types of Crystals
Metallic Crystals
Lattice points occupied by metal atoms
Held together by metallic bonds
Soft to hard, low to high melting point
Good conductors of heat and electricity
11.6
Cross Section of a Metallic Crystalnucleus &
inner shell e-
mobile seaof e-
amorphous sol id
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An amorphoussol iddoes not possess a well-defined
arrangement and long-range molecular order.
A glassis an optically transparent fusion product of inorganicmaterials that has cooled to a rigid state without crystallizing
Crystalline
quartz (SiO2)
Non-crystalline
quartz glass 11.7
amorphoussol id
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The boi l ing po intis the temperature at which the
(equilibrium) vapor pressure of a liquid is equal to the
external pressure.
The normal boi l ing po intis the temperature at which a liquid
boils when the external pressure is 1 atm.
11.8
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On top of a mountain
Water boils at a lower temp. on top of a mountain than
at sea level. Why? because the external pressure (atmospheric
pressure) is less on top of a mountain.
In an autoclave
An autoclave is used to sterilize medical instruments The pressure is often 2 atmospheres.
Will water inside the autoclave boil at 100C?
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Molar heat of vaporizat ion (DHvap) is the energy required to
vaporize 1 mole of a liquid at its boiling point.
ln P= -DHvap
RT+ C
Clausius-Clapeyron Equation
P= (equilibrium) vapor pressure
T= temperature (K)
R= gas constant (8.314 J/Kmol)
11.8
Vapor Pressure Versus Temperature
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Molar heat of fus ion (DHfus) is the energy required to melt
1 mole of a solid substance at its freezing point.
11.8
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11.8
Heating Curve Heat of fusion = energy
needed to convert a solid
to a liquid
Heat of vaporization =
energy needed to
convert a liquid to a gas
Be able to draw a
heating curve
Energy is needed to
heat a solid
heat a liquid
heat a gas convert a solid to a
liquid
convert a liquid to a gas
convert a solid to a gas
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A phase diagramsummarizes the conditions at which a
substance exists as a solid, liquid, or gas.
Phase Diagram of Water
11.9
phase diagram
Triple point
All three
phases are in
equilibrium
Solid line:
Two phases arein equilibrium
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Phase Diagram of Water
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Es kering (dry ice)
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