Gaya Antar Molekul Dan Cairan Dan Padatan

7/21/2019 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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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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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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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


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


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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