Deck 12: Intermolecular Forces: Liquids,solids,and Phase Changes

Question 1

Consider the following phase diagram and identify the process occurring as one goes from point C to point D.

A)increasing temperature with a phase change from solid to liquid
B)increasing temperature with a phase change from solid to vapor
C)increasing temperature with a phase change from liquid to vapor
D)increasing temperature with no phase change
E)increasing temperature beyond the critical point

Answer 1

increasing temperature with a phase change from solid to vapor

Question 2

Examine the following phase diagram and identify the feature represented by point A.

A)melting point
B)critical point
C)triple point
D)sublimation point
E)boiling point

Answer 2

triple point

Question 3

Diethyl ether,used as a solvent for extraction of organic compounds from aqueous solutions,has a high vapor pressure which makes it a potential fire hazard in laboratories in which it is used.How much energy is released when 100.0 g is cooled from 53.0°C to 10.0°C?

A)10.1 kJ
B)13.1 kJ
C)16.1 kJ
D)45.2 kJ
E)48.6 kJ

Answer 3

48.6 kJ

Question 4

Examine the following phase diagram and identify the feature represented by point B.

A)melting point
B)triple point
C)critical point
D)sublimation point
E)boiling point

Question 5

Neon condenses due to

A)dipole-dipole forces.
B)London dispersion forces.
C)hydrogen bonding.
D)covalent bonding.
E)intramolecular forces.

Question 6

Examine the following phase diagram and determine what phase exists at point F.

A)vapor + liquid
B)vapor
C)liquid
D)solid
E)supercritical fluid

Question 7

Examine the phase diagram for the substance Bogusium (Bo)and select the correct statement.

A)Bo(s)has a lower density than Bo(l).
B)The triple point for Bo is at a higher temperature than the melting point for Bo.
C)Bo changes from a solid to a liquid as one follows the line from C to D.
D)Bo changes from a liquid to a gas as one follows the line from C to D.
E)Point B represents the critical temperature and pressure for Bo.

Question 8

Octane has a vapor pressure of 40.torr at 45.1°C and 400.torr at 104.0°C.What is its heat of vaporization?

A)39.0 kJ/mol
B)46.0 kJ/mol
C)590 kJ/mol
D)710 kJ/mol
E)None of these choices is correct.

Question 9

In hydrogen iodide __________________ are the most important intermolecular forces.

A)dipole-dipole forces
B)London dispersion forces
C)hydrogen bonding
D)covalent bonds
E)polar covalent bonds

Question 10

Pentane,C₅H₁₂,boils at 35°C.Which of the following is true about kinetic energy,E_k,and potential energy,E_p,when liquid pentane at 35°C is compared with pentane vapor at 35°C?

A)E_k(g)< E_k(l);E_p(g) $\approx$ E_p(l)
B)E_k(g)> E_k(l);E_p(g) $\approx$ E_p(l)
C)E_p(g)< E_p(l);E_k(g) $\approx$ E_k(l)
D)E_p(g)> E_p(l);E_k(g) $\approx$ E_k(l)
E)E_p(g) $\approx$ E_p(l);E_k(g) $\approx$ E_k(l)

Question 11

Liquid sodium can be used as a heat transfer fluid.Its vapor pressure is 40.0 torr at 633°C and 400.0 torr at 823°C.Calculate its heat of vaporization.

A)43.4 kJ/mol
B)52.5 kJ/mol
C)70.6 kJ/mol
D)1.00 $\times$ 10² kJ/mol
E)None of these choices is correct.

Question 12

Liquid ammonia (boiling point = -33.4°C)can be used as a refrigerant and heat transfer fluid.How much energy is needed to heat 25.0 g of NH₃(l)from -65.0°C to -12.0°C?

A)5.5 kJ
B)6.3 kJ
C)39 kJ
D)340 kJ
E)590 kJ

Question 13

Octane is a component of fuel used in internal combustion engines.The dominant intermolecular forces in octane are

A)dipole-dipole forces.
B)London dispersion forces.
C)hydrogen bonding.
D)covalent bonds.
E)carbon-hydrogen bonds.

Question 14

Which one of the following quantities is generally not obtainable from a single heating or cooling curve of a substance,measured at atmospheric pressure?

A)melting point
B)boiling point
C)triple point
D)heat of fusion
E)heat of vaporization

Question 15

Ammonia's unusually high melting point is the result of

A)dipole-dipole forces.
B)London dispersion forces.
C)hydrogen bonding.
D)covalent bonding.
E)ionic bonding.

Question 16

Which of the following is true about kinetic energy,E_k,and potential energy,E_p,when ethyl alcohol at 40°C is compared with ethyl alcohol at 20°C?

A)E_k(40°C)< E_k(20°C);E_p(40°C) $\approx$ E_p(20°C)
B)E_k(40°C)> E_k(20°C);E_p(40°C) $\approx$ E_p(20°C)
C)E_p(40°C)< E_p(20°C);E_k(40°C) $\approx$ E_k(20°C)
D)E_p(40°C)> E_p(20°C);E_k(40°C) $\approx$ E_k(20°C)
E)E_p(40°C)> E_p(20°C);E_k(40°C)> E_k(20°C)

Question 17

A sample of octane in equilibrium with its vapor in a closed 1.0-L container has a vapor pressure of 50.0 torr at 45°C.The container's volume is increased to 2.0 L at constant temperature and the liquid/vapor equilibrium is reestablished.What is the vapor pressure?

A)> 50.0 torr
B)50.0 torr
C)25.0 torr
D)The mass of the octane vapor is needed to calculate the vapor pressure.
E)The external pressure is needed to calculate the vapor pressure.

Question 18

Which of the following atoms should have the greatest polarizability?

A)F
B)Br
C)Po
D)Pb
E)He

Question 19

The phase diagram for xenon has a solid-liquid curve with a positive slope.Which of the following is true?

A)Solid xenon has a higher density than liquid xenon.
B)Solid xenon has the same density as liquid xenon.
C)The phase diagram cannot be used to predict which phase of xenon is denser.
D)Freezing xenon is an endothermic process.
E)None of these statements is true.

Question 20

When the electron cloud of a molecule is easily distorted,the molecule has a high

A)polarity.
B)polarizability.
C)dipole moment.
D)van der Waals radius.
E)compressibility.

Question 21

The strongest intermolecular interactions between hydrogen sulfide (H₂S)molecules arise from

A)dipole-dipole forces.
B)London dispersion forces.
C)hydrogen bonding.
D)ion-dipole interactions.
E)disulfide linkages.

Question 22

Which of the following atoms should have the smallest polarizability?

A)Si
B)S
C)Te
D)Bi
E)Br

Question 23

Which of the following substances will have hydrogen bonds between molecules?

A)(CH₃)₃N
B)CH₃-O-CH₃
C)CH₃CH₂-OH
D)CH₃CH₂-F
E)HI

Question 24

The energy needed to increase the surface area of a liquid is

A)capillary action.
B)surface tension.
C)viscosity.
D)cohesion.
E)specific elasticity.

Question 25

Which of the following terms refers to the resistance of a liquid to flow?

A)surface tension
B)capillary action
C)viscosity
D)adhesion
E)cohesion

Question 26

Which of the following should have the highest surface tension at a given temperature?

A)a
B)b
C)c
D)d
E)e

Question 27

In which of the following compounds will the molecules not form hydrogen bonds with each other?

A)a
B)b
C)c
D)d
E)e

Question 28

Which of the following pairs is arranged with the particle of higher polarizability listed first?

A)CCl₄,CI₄
B)H₂O,H₂Se
C)C₆H₁₄,C₄H₁₀
D)NH₃,NF₃
E)None of these choices is correct.

Question 29

Select the pair of substances in which the one with the lower vapor pressure at a given temperature is listed first.

A)a
B)b
C)c
D)d
E)e

Question 30

The strongest intermolecular interactions between pentane (C₅H₁₂)molecules arise from

A)dipole-dipole forces.
B)London dispersion forces.
C)hydrogen bonding.
D)ion-dipole interactions.
E)carbon-carbon bonds.

Question 31

Comparing the energies of the following intermolecular forces on a kJ/mol basis,which would normally have the highest energy (i.e. ,be the strongest force)?

A)ion-induced dipole
B)dipole-induced dipole
C)ion-dipole
D)dipole-dipole
E)dispersion

Question 32

Which of the following pairs is arranged with the particle of higher polarizability listed first?

A)Se^2-,S^2-
B)I,I^-
C)Mg²⁺,Mg
D)Br,I
E)None of these choices is correct.

Question 33

When the adhesive forces between a liquid and the walls of a capillary tube are greater than the cohesive forces within the liquid

A)the liquid level in a capillary tube will rise above the surrounding liquid and the surface in the capillary tube will have a convex meniscus.
B)the liquid level in a capillary tube will rise above the surrounding liquid and the surface in the capillary tube will have a concave meniscus.
C)the liquid level in a capillary tube will drop below the surrounding liquid and the surface in the capillary tube will have a convex meniscus.
D)the liquid level in a capillary tube will drop below the surrounding liquid and the surface in the capillary tube will have a concave meniscus.
E)None of these will occur.

Question 34

Which of the following has a boiling point which does not fit the general trend?

A)NH₃
B)PH₃
C)AsH₃
D)SbH₃
E)BiH₃

Question 35

The strongest intermolecular interactions between hydrogen fluoride (HF)molecules arise from

A)dipole-dipole forces.
B)London dispersion forces.
C)hydrogen bonding.
D)ion-dipole interactions.
E)ionic bonds.

Question 36

Select the pair of substances in which the one with the higher vapor pressure at a given temperature is listed first.

A)C₇H₁₆,C₅H₁₂
B)CCl₄,CBr₄
C)H₂O,H₂S
D)CH₃CH₂OH,CH₃-O-CH₃
E)Xe,Kr

Question 37

The strongest intermolecular interactions between ethyl alcohol (CH₃CH₂OH)molecules arise from

A)dipole-dipole forces.
B)London dispersion forces.
C)hydrogen bonding.
D)ion-dipole interactions.
E)carbon-oxygen bonds.

Question 38

Which of the following should have the highest boiling point?

A)CF₄
B)CCl₄
C)CBr₄
D)CI₄
E)CH₄

Question 39

Which of the following should have the highest surface tension at a given temperature?

A)CH₄
B)CF₄
C)CCl₄
D)CBr₄
E)CI₄

Question 40

Which of the following should have the lowest boiling point?

A)C₅H₁₂
B)C₆H₁₄
C)C₈H₁₈
D)C₁₀H₂₂
E)C₁₂H₂₆

Question 41

Which of the following statements about the packing of monatomic solids with different unit cells is incorrect?

A)The coordination number of atoms in hcp and fcc structures is 12.
B)The coordination number of atoms in simple cubic structures is 6.
C)The coordination number of atoms in bcc structures is 8.
D)A bcc structure has a higher packing efficiency than a simple cubic structure.
E)A bcc structure has a higher packing efficiency than a fcc structure.

Question 42

Which of the following factors contributes to a low viscosity for a liquid?

A)low temperature
B)spherical molecular shape
C)hydrogen bonding
D)high molecular weight
E)high boiling point

Question 43

Which of the following pairs of substances is arranged so that the one with higher viscosity is listed first?

A)a
B)b
C)c
D)d
E)None of these choices is correct.

Question 44

A metal such as chromium in the face-centered cubic lattice will have ________________ atom(s)per unit cell.

A)1
B)2
C)3
D)4
E)10

Question 45

A metal in the simple cubic lattice will have ________________ atom(s)per unit cell.

A)1
B)2
C)3
D)4
E)8

Question 46

Which of the following liquid substances would you expect to have the lowest surface tension?

A)Pb
B)CH₃OCH₃
C)HOCH₂CH₂OH
D)H₂O
E)CH₃CH₂OH

Question 47

For the solid forms of the following elements,which one is most likely to be of the molecular type?

A)Xe
B)C
C)Pb
D)S
E)Cr

Question 48

A metal such as chromium in the body-centered cubic lattice will have _______________ atom(s)per unit cell.

A)1
B)2
C)3
D)4
E)9

Question 49

Polonium crystallizes in the simple cubic lattice.What is the coordination number for Po?

A)3
B)4
C)6
D)8
E)12

Question 50

In an ionic solid MX consisting of the monatomic ions,M⁺ and X^-,the coordination number of M⁺ is _______________.

A)1
B)2
C)6
D)8
E)impossible to predict without knowing the crystal structure of MX

Question 51

Which of the following statements concerning a face-centered cubic unit cell and the corresponding lattice,made up of identical atoms,is incorrect?

A)The coordination number of the atoms in the lattice is 8.
B)The packing in this lattice is more efficient than for a body-centered cubic system.
C)If the atoms have radius r,then the length of the cube edge is $\sqrt 8$ $\times$ r.
D)There are four atoms per unit cell in this type of packing.
E)The packing efficiency in this lattice and hexagonal close packing are the same.

Question 52

Iron crystallizes in the body-centered cubic lattice.What is the coordination number for Fe?

A)4
B)6
C)8
D)10
E)12

Question 53

Which of the following liquids is likely to have the highest surface tension?

A)Br₂
B)C₈H₁₈
C)CH₃OCH₃
D)CH₃OH
E)Pb

Question 54

Lead crystallizes in the face-centered cubic lattice.What is the coordination number for Pb?

A)4
B)6
C)8
D)10
E)12

Question 55

Which one of the following statements about unit cells and packing in solids is incorrect?

A)In any unit cell of a solid crystal,each face of the cell must have an opposite face which is equal and parallel to it.
B)The faces of a unit cell must all be at angles of 90° to each other.
C)The coordination number of atoms in a close packed metal is 12.
D)The packing efficiency in fcc structures is higher than in bcc structures.
E)The packing efficiency in fcc and hcp structures is the same.

Question 56

Which one of the following substances does not exist in the indicated solid type?

A)graphite - network
B)Na - metallic
C)SiO₂ - molecular
D)NaCl - ionic
E)diamond - network

Question 57

When liquid bromine is cooled to form a solid,which of the following types of solid would it form?

A)atomic
B)metallic
C)molecular
D)ionic
E)covalent network

Question 58

A temperature increase causes __________________ in the conductivity of a semiconductor.

A)a decrease
B)an increase
C)a modulation
D)an increase or decrease (depending on the semiconductor)
E)no change

Question 59

The coordination number of sodium and chloride ions in the NaCl lattice,are,respectively:

A)10 and 10
B)8 and 8
C)6 and 6
D)4 and 4
E)None of these choices is correct.

Question 60

A cubic unit cell has an edge length of 400.pm.The length of its body diagonal (internal diagonal)in pm is therefore

A)512
B)566
C)631
D)693
E)724

Question 61

Assuming that atoms are spherical,calculate the fraction of space which is occupied by atoms (i.e. ,the packing efficiency)in a metal with a face-centered cubic unit cell.

Question 62

Iron has a body-centered cubic unit cell,and a density of 7.87 g/cm³.Calculate the edge length of the unit cell,in pm.(The atomic mass of iron is 55.85 amu.Also,1 amu = 1.661 $\times$ 10^-24g. )

Question 63

Assuming that atoms are spherical,calculate the fraction of space which is occupied by atoms (i.e. ,the packing efficiency)in a metal with a simple cubic unit cell.

Question 64

Strontium metal crystallizes in a cubic unit cell which has an edge length of 612 pm.If the mass of an atom of Sr is 87.62 amu,and the density of Sr metal is 2.54 g/cm³,calculate the number of atoms per unit cell.(1 amu = 1.661 $\times$ 10^-24 g. )

Question 65

a.Name the two unit cells which occur in close packing of identical atoms.
b.Briefly explain how the two types of close-packed lattices of identical atoms differ,in terms of atomic arrangements.

Question 66

The energy gap between the conduction band and the valence band is large for

A)conductors.
B)semiconductors.
C)superconductors.
D)insulators.
E)alloys.

Question 67

Of the five major types of crystalline solid,which would you expect each of the following to form? (e.g. ,H₂O: molecular)
a.Sn
b.Si
c.KCl
d.Xe
e.F₂

Question 68

How do the electrical properties of semiconductors differ from those of metals?

Question 69

The density of solid sodium chloride,NaCl,is 2.17 g/cm³.Use your knowledge of the sodium chloride lattice to calculate the spacing between Na⁺ and Cl^- nearest neighbors,in cm.(Atomic masses (amu)are: Na,22.99;Cl,35.45.Also,1 amu = 1.661 $\times$ 10^-24 g)

Question 70

Draw a fully labeled phase diagram (P versus T)of a substance whose solid phase can melt due to applied pressure (i.e. ,solid is less dense than liquid).Clearly label the triple point and the critical temperature on your diagram.

Question 71

The vapor pressure of 1-butene is 1.268 atm at 273.15 K and its heat of vaporization is 22.9 kJ/mol.What is the normal boiling point of 1-butene?

Question 72

a.Explain what is meant by the term "unit cell".
b.Copper metal has a face-centered cubic unit cell.The edge length of the unit cell is 361 pm,and the atomic weight of copper is 63.55 amu.Calculate the density of the copper in g/cm³.
(1 amu = 1.661 $\times$ 10^-24 g. )
c.From the data in (b),calculate the radius of a copper atom in pm.

Question 73

Chlorine trifluoride is used in processing nuclear reactor fuel.It has a vapor pressure of 29.1 torr at -47.0°C and its heat of vaporization is 30.61 kJ/mol.At what temperature would its vapor pressure be 107.7 torr?

Question 74

a.State the essential requirements for hydrogen bonding to be important in a compound.
b.List four properties of water which are significantly influenced by the presence of hydrogen bonding.

Question 75

The highest temperature at which superconductivity has been achieved is approximately

A)4 K
B)30 K
C)70 K
D)100 K
E)130 K

Question 76

Mercury melts at -39°C and boils at 357°C.Draw a diagram of the heating curve of mercury.Label all lines and axes,and clearly indicate the melting and boiling points on your diagram.

Question 77

Consider the phase diagram shown below.
a.What phase(s)is/are present at point A?
b.What phase(s)is/are present at point B?
c.Name point C and explain its significance.
d.Starting at D,if the pressure is lowered while the temperature remains constant,describe what will happen.

Question 78

Use molecular orbital band diagrams to explain why metals are good conductors but semiconductors are not.

Question 79

Liquid ammonia boils at -33.4°C and has a heat of vaporization of 23.5 kJ/mol.Calculate its vapor pressure at -50.0°C.

Question 80

A temperature increase causes __________________ in the conductivity of a conductor.

A)a decrease
B)an increase
C)an increase or decrease (depending on the conductor)
D)a modulation
E)no change