Chapter 11 Flashcards

1
Q

The vapor pressure of a liquid at a particular temperature is the

A

the partial pressure of the vapor over the liquid measured at equilibrium.

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2
Q

The vapor pressure depends on the

A

liquid and on the temperature.

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3
Q

boiling point

A

the temperature at which the vapor pressure is equal to the pressure on the liquid, usually atmospheric pressure. At this temperature, bubbles of gas form within the liquid.

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4
Q

The normal boiling point is measured at

A

1-atmosphere pressure.

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5
Q

When the pressure on the liquid increases, as is the case with a pressure cooker, the boiling point

A

increases

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6
Q

when the pressure on the liquid decreases, as is the case at high altitude, the boiling point

A

decreases

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7
Q

freezing point

A

the temperature at which a pure liquid changes to a crystalline solid (or freezes)

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8
Q

melting point

A

the temperature at which a crystalline solid changes to a liquid (or melts).

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9
Q

heat of fusion

A

the heat needed to melt a solid. It is given in kJ/mol

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10
Q

heat of vaporization

A

the heat needed to vaporize a liquid. It is given in kJ/mol

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11
Q

The Clausius–Clapeyron equation

A

can be used to find the vapor pressure, the heat of vaporization, or the temperature.

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12
Q

phase diagram

A

graphical way to summarize the conditions under which the various states of a substance are stable. •In a phase diagram, phases are separated by lines that represent equilibrium between those phases

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13
Q

triple point

A

the point where all three phases are in equilibrium.

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14
Q

critical point

A

gives the temperature (critical temperature, TC) at which the liquid state can no longer exist and the pressure at that temperature (critical pressure). Above this temperature and pressure, there is only one state, a supercritical fluid.

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15
Q

Surface tension

A

the energy required to increase the surface area of a liquid by a unit amount. The values are given in J/m2.

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16
Q

Surface tension arises because

A

the molecules at the surface of a liquid experience a net force toward the center of the liquid.

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17
Q

is the property that allows insects to walk on the surface of water or a pin to float

A

surface tension

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18
Q

viscosity

A

is the resistance to flow exhibited by liquids and gases

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19
Q

the 3 types of intermolecular forces

A

Dipole-Dipole forces, London forces, Hydrogen bonding forces

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20
Q

van der waals forces

A

a general term that includes both dipole-dipole forces and London forces.

  • no dipole-dipole force in nonpolar molecules
  • but there is still a force of attraction
  • Fritz London explained this relationship and is now call the London forces
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21
Q

polar molecules exhibit

A

dipole-dipole forces that result in alignment of the molecules

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22
Q

London (dispersion) forces (LDF) in a non polar molecule

A

the charge is uniformly distributed over time. But in any one instant, the charge is not uniformly distributed. In that instant, there is an instantaneous dipole. To see how this works, let’s look at a neon atom

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23
Q

The instantaneous dipole of the neon atom induces an

A

instantaneous dipole in adjacent atoms, resulting in an attractive force between them.

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24
Q

how do instantaneous dipoles usually change

A

However, the instantaneous dipoles tend to change together,maintaining the attractive force between them.

25
Q

London (dispersion) forces (LDF)

A
  • London forces are the weak attractive forces between molecules resulting from the small, instantaneous dipoles that occur because of the varying positions of the electrons during their motion about the nuclei.
  • All molecules exhibit London forces.
26
Q

london forces increase with

A

increasing mass (atomic number) because the presence of more electrons causes a stronger instantaneous dipole.

27
Q

the more polarized the LDF . . .

A

the more easily distorted the molecules will be

28
Q

______ compounds have the strongest intermolecular forces and the highest heat of vaporization because it is most flexible and, therefore, most polarizable.

A

straight-chain compounds

29
Q

The most _____ compound has the weakest intermolecular forces and the lowest heat of vaporization

A

compact

30
Q

The stronger the intermolecular forces, the

A

higher the heat of vap

31
Q

the lower the vapor pressure at any given temperature, the

A

higher the surface tension and the more viscous the liquid is

32
Q

Each molecule has one or more

A

-OH group

33
Q

Molecules with this group (-OH) have an additional force called the

A

hydrogen bonding force

34
Q

Hydrogen bonding

A

is a weak attractive force that exists between hydrogen atoms bonded to a very electronegative atom, X, and a lone pair of electrons on another small, electronegative atom, Y.

35
Q

Most often, X is __, ___, or ___, the smallest, most electronegative elements.

A

F, O, or N,

36
Q

A solid is a nearly incompressible state of matter with a well-defined shape, because

A

the units (atoms, molecules, ions) making up the solid are in close contact and reside in fixed positions or sites.

37
Q

molecular solid

A

consists of atoms or molecules. It is held together by intermolecular forces.

38
Q

metallic solid

A

consists of the positive cores of metal atoms. It is held together by metallic bonding, a “sea” of delocalized electrons.

39
Q

ionic solid

A

composed of cations and anions. It is held together by ionic bonds, the electrical attractions between oppositely charged particles

40
Q

covalent network solid

A

consists of atoms. These atoms are held together in large chains or networks by covalent bonds.

41
Q

Carbon exists as a _______ solid in both the graphite and diamond forms

A

covalent network

42
Q

In general, molecular solids have _____

A

lower melting points

43
Q

covalent network solids and ionic solids have ___________

A

high melting points

44
Q

The melting points of ionic solids vary owing to differences in

A

lattice energy that reflect the charge and sizes of the ions involved.

45
Q

The melting points of metals

A

vary widely

46
Q

Hardness depends on

A

how easily the structural units can be moved relative to one another.

47
Q

Molecular solids tend to be

A

soft

48
Q

Covalent network solids, such as diamond, are

A

very hard

49
Q

Ionic compounds are _____ because they tend to fracture easily along crystal planes.

A

brittle

50
Q

Metals are ______ so that they can be easily shaped by hammering

A

malleable

51
Q

Metals are good electrical conductors because of

A

their delocalized valence electrons.

52
Q

Ionic solids do not______. When melted, however, they ____. They also conduct electricity when ________

A

conduct electricity; do conduct electricity: they are dissolved in water.

53
Q

crystalline solid

A

composed of one or more crystals with a well-defined ordered structure in three dimensions

54
Q

amorphous solid (and an example)

A

has a disordered structure and lacks a well-defined arrangement of basic units.

Glass is an amorphous solid obtained by cooling a liquid rapidly enough that its basic units are “frozen” in random positions before they can assume a crystalline arrangement

55
Q

crystal lattice

A

is the geometric arrangement of lattice points of a crystal in which we choose one lattice point at the same location within each of the basic units of the crystal

56
Q

cubic crystal (3 possible unit cells)

A

There are three possible unit cells: simple cubic, body-centered cubic, and face-centered cubic.

57
Q

simple cubic (Coordination Number and Number of Atoms Per Unit Cell)

A

CN=6

atom/unit cell(8 x 1/8 = 1)

58
Q

body-centered cubic (Coordination Number and Number of Atoms Per Unit Cell)

A

CN=8

2 atoms/unit cell(8 x 1/8 + 1 = 2)

59
Q

face-centered cubic (Coordination Number and Number of Atoms Per Unit Cell)

A

CN=12

atoms/unit cell(8 x 1/8 + 6 x 1/2 = 4)