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

Question 1

Liquid ammonia (boiling point = -33.4 $\degree$ 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 $\degree$ C to -12.0 $\degree$ C?
Specific heat capacity, NH₃(l) : 4.7 J/(g ? K)
Specific heat capacity, NH₃(g): 2.2 J/(g ? K)
Heat of vaporization: 23.5 kJ/mol
Molar mass, ?: 17.0 g/mol

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

Answer 1

39 kJ

Question 2

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

Answer 2

E_p(g) > E_p(l); E_k(g) $\approx$ E_k(l)

Question 3

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.

Answer 3

London dispersion forces.

Question 4

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

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

Question 5

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

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

Question 6

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 $\degree$ C to 10.0 $\degree$ C?
Boiling point: 34.5 $\degree$ C
Heat of vaporization: 351 J/g
Specific heat capacity, (CH₃)₂O(l): 3.74 J/(g ? K)
Specific heat capacity, (CH₃)₂O(g): 2.35 J/(g ? K)

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

Question 7

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 8

Neon atoms are attracted to each other by

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

Question 9

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 10

Which of the following atoms should have the smallest polarizability?

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

Question 11

The normal boiling point of ether is 307.8 K. Calculate the temperature at which its vapor pressure is exactly half of that at its normal boiling point. The heat of vaporization for ether is 26.69 kJ/mol.

A) 305 K
B) 302 K
C) 295 K
D) 289 K
E) 281 K

Question 12

A 5.00 g sample of water vapor, initially at 155 $\degree$ C is cooled at atmospheric pressure, producing ice at -55 $\degree$ C. Calculate the amount of heat energy lost by the water sample in this process, in kJ. Use the following data: specific heat capacity of ice is 2.09 J/g ? K; specific heat capacity of liquid water is 4.18 J/g ? K; specific heat capacity of water vapor is 1.84 J/g ? K; heat of fusion of ice is 336 J/g; heat of vaporization of water is 2260 J/g.

A) 15.6 kJ
B) 10.2 kJ
C) 5.4 kJ
D) 3.2 kJ
E) 1.6 kJ

Question 13

Which of the following atoms should have the greatest polarizability?

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

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

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 $\degree$ 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 16

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 choices is correct.

Question 17

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 18

The Clausius-Clapeyron equation is used in calculations of

A) melting and freezing points.
B) vapor pressures of liquids.
C) osmotic pressures of solutions.
D) heats of vaporization at different temperatures.
E) crystal structure.

Question 19

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 20

Octane has a vapor pressure of 40. torr at 45.1 $\degree$ C and 400. torr at 104.0 $\degree$ 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 21

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 22

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

A)
B)
C)
D)
E)

Question 23

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 choices is correct.

Question 24

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 25

Which of the following pairs of molecules can form hydrogen bonds between them?

A) HCl and HI
B) CH₃OH and NH₃
C) CH₄ and H₂O
D) SO₂ and CH₂O
E) H₂ and O₂

Question 26

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 27

Which one 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 28

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 29

Which of the following should have the highest boiling point?

A) CF₄
B) CCl₄
C) CBr₄
D) CI₄
E) CH₄

Question 30

The meniscus of mercury in a glass capillary tube is convex because of

A) the very high density of mercury as compared with water.
B) the low surface tension of mercury.
C) the greater attraction of mercury atoms to the glass than to each other.
D) the weaker attraction of mercury atoms to the glass than to each other.
E) electrostatic repulsion between the glass and the mercury.

Question 31

Which of the following should have the lowest boiling point?

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

Question 32

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 33

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 34

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 35

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

A) and CH₃CH₂CH₂OH
B) PH₃ and NH₃
C) CF₄ and CBr₄
D) C₃H₈ and C₄H₁₀
E) F₂ and Cl₂

Question 36

Which of the following properties measures the energy needed to increase the surface area of a liquid?

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

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

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

A)
B)
C)
D)
E)

Question 39

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 40

What types of forces exist between molecules of CO₂?

A) hydrogen bonding only.
B) hydrogen bonding and dispersion forces.
C) dipole-dipole forces only.
D) dipole-dipole and dispersion forces.
E) dispersion forces only.

Question 41

Crystal structures may be conveniently measured using

A) X-ray diffraction.
B) infrared spectroscopy.
C) ultraviolet-visible spectroscopy.
D) microwave spectroscopy.
E) magnetic resonance imaging.

Question 42

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

A) Br₂
B) C₈H₁₈
C) CH₃OCH₃
D) CH₃OH
E) Pb

Question 43

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 44

When identical particles pack in a simple cubic lattice, there is/are ____ particle(s) per unit cell.

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

Question 45

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 46

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

A)
B)
C)
D)
E) None of these choices is correct.

Question 47

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 * 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 48

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 49

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 50

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 51

A metal such with a face-centered cubic lattice will have ________________ atom(s) per unit cell.

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

Question 52

A metal with a body-centered cubic lattice will have ______ atom(s) per unit cell.

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

Question 53

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 54

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 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 $\degree$ 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

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 57

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 58

A certain solid metallic element has a density 7.87 g/cm³ and a molar mass of 55.85 g/mol. It crystallizes with a cubic unit cell, with an edge length of 286.7 pm. Calculate the number of atoms per unit cell.

A) 1
B) 2
C) 3
D) 4
E) 6

Question 59

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 60

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 61

Which of the following statements about ceramics is incorrect?

A) Silicon carbide has a diamond-like structure.
B) Boron nitride can exist in both diamond-like and graphite-like forms.
C) Silicon carbide can be prepared by direct reaction of silicon and carbon.
D) Superconducting ceramics present manufacturing difficulties owing to their brittleness.
E) Superconducting ceramic compounds usually incorporate cobalt in a key role.

Question 62

List the three common classes of liquid crystals in order of decreasing degree of order.

Question 63

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

Question 64

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 65

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 66

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 67

Mercury melts at -39 $\degree$ C and boils at 357 $\degree$ 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 68

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

Question 69

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 70

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

Question 71

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 72

, the device/material produced is a/an

A) intrinsic semiconductor.
B) p-type semiconductor.
C) n-type semiconductor.
D) p-n junction.
E) transistor.

Question 73

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 74

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 75

What word best describes the type of liquid crystal represented in this figure?

A) nematic
B) cholesteric
C) smectic
D) isotropic
E) elastic

Question 76

The phase diagram of a substance shows the energy changes associated with changes of state.

Question 77

What adjective best describes the solid compound IF₇?

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

Question 78

The maximum number of phases of a single substance which can coexist in equilibrium is two.

Question 79

Germanium is a semiconductor. With the aid of diagrams showing bands of molecular orbital, explain why it is a poor conductor and how doping it with phosphorus increases its conductivity.

Question 80

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.