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

Question 1

In cubic closest packing, the unit cell is body-centered cubic.

Answer 1

False

Question 2

In a transistor, the current through one semiconductor junction controls the current through a neighboring junction.

Answer 2

True

Question 3

In the packing of identical atoms with cubic unit cells, the packing efficiency increases as the coordination number increases.

Answer 3

True

Question 4

Liquid crystal displays are most commonly constructed of smectic type liquid crystals.

Question 5

The phase diagram of a substance can be used to obtain the vapor pressure of that substance at a given temperature.

Question 6

The surface tension of water is lowered when a detergent is present in solution.

Question 7

In metals, the conduction bands and valence bands of the molecular orbitals are separated by a large energy gap.

Question 8

A single water molecule can participate in at most two hydrogen bonds at any instant.

Question 9

Smectic liquid crystals are more highly ordered than either nematic or cholesteric liquid crystals.

Question 10

A liquid may be made to boil at room temperature, simply by lowering the pressure.

Question 11

All gases can be liquefied at room temperature simply by increasing the pressure on the gas.

Question 12

Hexagonal close packing of identical atoms occurs when close-packed layers are stacked in an abcabc... arrangement.

Question 13

If the solid form of a pure substance is denser than its liquid form, an increase in pressure will cause the melting point to decrease.

Question 14

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

Question 15

Ceramic superconductors often contain copper in unusual oxidation states.

Question 16

Only molecules that do not have dipole moments can experience dispersion forces.

Question 17

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)≈ E _p( l)
B)E _k( g)> E _k( l); E _p( g)≈ E _p( l)
C)E _p( g)< E _p( l); E _k( g)≈ E _k( l)
D)E _p( g)> E _p( l); E _k( g)≈ E _k( l)
E)E _p( g)≈ E _p( l); E _k( g)≈ E _k( l)

Question 18

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

Question 19

The energy of a hydrogen bond is greater than that of a typical covalent bond.

Question 20

Some of the information obtained from the heating or cooling curve of a substance can also be found on a phase diagram of that substance.

Question 21

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

Question 22

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 23

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 24

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 25

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 26

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 27

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 28

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 × 10 ² kJ/mol
E)None of these choices are correct.

Question 29

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

Question 30

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 are correct.

Question 31

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 32

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 33

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 34

A 5.00 g sample of water vapor, initially at 155°C is cooled at atmospheric pressure, producing ice at −55°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 35

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 36

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 are correct.

Question 37

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 38

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

Question 39

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)≈ E _p(20°C)
B)E _k(40°C)> E _k(20°C); E _p(40°C)≈ E _p(20°C)
C)E _p(40°C)< E _p(20°C); E _k(40°C)≈ E _k(20°C)
D)E _p(40°C)> E _p(20°C); E _k(40°C)≈ E _k(20°C)
E)E _p(40°C)> E _p(20°C); E _k(40°C)> E _k(20°C)

Question 40

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 41

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

A)HCl and HI
B)CH ₃OH and NH ₃
C)CH ₄ and H ₂O
D)SO ₂ and CH ₂O
E)H ₂ and O ₂

Question 42

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

A)(CH ₃)₃N
B)CH ₃-O-CH ₃
C)CH ₃CH ₂-OH
D)CH ₃CH ₂-F
E)HI

Question 43

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

A)
B)
C)
D)
E)

Question 44

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

A)Se ²⁻, S ²⁻
B)I, I ⁻
C)Mg ²⁺, Mg
D)Br, I
E)None of these choices are correct.

Question 45

Which of the following should have the lowest boiling point?

A)C ₅H ₁₂
B)C ₆H ₁₄
C)C ₈H ₁₈
D)C ₁₀H ₂₂
E)C ₁₂H ₂₆

Question 46

Which of the following should have the highest boiling point?

A)CF ₄
B)CCl ₄
C)CBr ₄
D)CI ₄
E)CH ₄

Question 47

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 48

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 49

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 50

Which of the following atoms should have the greatest polarizability?

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

Question 51

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

A)
B)
C)
D)
E)

Question 52

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

A)C ₇H ₁₆, C ₅H ₁₂
B)CCl ₄, CBr ₄
C)H ₂O, H ₂S
D)CH ₃CH ₂OH, CH ₃-O-CH ₃
E)Xe, Kr

Question 53

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 54

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 55

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 56

Which of the following atoms should have the smallest polarizability?

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

Question 57

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

A)CCl ₄, CI ₄
B)H ₂O, H ₂Se
C)C ₆H ₁₄, C ₄H ₁₀
D)NH ₃, NF ₃
E)None of these choices are correct.

Question 58

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

A)NH ₃
B)PH ₃
C)AsH ₃
D)SbH ₃
E)BiH ₃

Question 59

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 60

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

A)CH ₄
B)CF ₄
C)CCl ₄
D)CBr ₄
E)CI ₄

Question 61

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

A)
B)
C)
D)
E)

Question 62

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 63

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 64

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

A)Pb
B)CH ₃OCH ₃
C)HOCH ₂CH ₂OH
D)H ₂O
E)CH ₃CH ₂OH

Question 65

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 √8 × 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 66

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 are correct.

Question 67

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)E

Question 68

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 69

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 70

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 71

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 72

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 73

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 74

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 75

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

A)Br ₂
B)C ₈H ₁₈
C)CH ₃OCH ₃
D)CH ₃OH
E)Pb

Question 76

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 77

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 78

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 79

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 80

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