Chemistry

Julia Burdge

Chapter 12

Intermolecular Forces and the Physical Properties of Liquids and Solids - all with Video Answers

Educators

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Chapter Questions

Problem 1

Give an example for each type of intermolecular force:
(a) dipole-dipole interaction, (b) ion-dipole interaction,
(c) dispersion forces, (d) van der Waals forces.

Shazia Naz

Shazia Naz

Numerade Educator

Problem 2

Explain the term polarizability. What kind of molecules tend to have high polarizabilities? What is the relationship between polarizability and intermolecular forces?

Jake Rempel

Numerade Educator

Problem 3

Explain the difference between a temporary dipole moment and a permanent dipole moment.

CE

Colter Ellis

Numerade Educator

Problem 4

What evidence can you cite that all molecules exert attractive forces on one another?

Shazia Naz

Numerade Educator

Problem 5

What physical properties are determined by the strength of intermolecular forces in solids and in liquids?

Shazia Naz

Numerade Educator

Problem 6

Explain why hydrogen bonding is exhibited by some hydrogen-containing compounds and not by others.

Shazia Naz

Numerade Educator

Problem 7

Describe the types of intermolecular forces that govern the folding of a protein molecule into its physiologically functioning three-dimensional state.

Shazia Naz

Numerade Educator

Problem 8

The compounds $\mathrm{Br}_{2}$ and $\mathrm{ICl}$ are isoelectronic (have the same number of electrons) and have similar molar masses, yet $\mathrm{Br}_{2}$ melts at $-7.2^{\circ} \mathrm{C}$ and ICl melts at $27.2^{\circ} \mathrm{C}$. Explain.

Shazia Naz

Numerade Educator

Problem 9

If you lived in Alaska, which of the following natural gases could you keep in an outdoor storage tank in winter: methane $\left(\mathrm{CH}_{4}\right)$ propane $\left(\mathrm{C}_{3} \mathrm{H}_{8}\right),$ or butane $\left(\mathrm{C}_{4} \mathrm{H}_{10}\right) ?$ Explain why.

Shazia Naz

Numerade Educator

Problem 10

The binary hydrogen compounds of the Group 4A elements and their boiling points are: $\mathrm{CH}_{4},-162^{\circ} \mathrm{C} ; \mathrm{SiH}_{4},-112^{\circ} \mathrm{C} ; \mathrm{GeH}_{4}$ $-88^{\circ} \mathrm{C} ;$ and $\operatorname{SnH}_{4},-52^{\circ} \mathrm{C} .$ Explain the increase in boiling points from $\mathrm{CH}_{4}$ to $\mathrm{SnH}_{4}$.

Shazia Naz

Numerade Educator

Problem 11

List the types of intermolecular forces that exist between molecules (or atoms or ions) in each of the following species:
(a) benzene $\left(\mathrm{C}_{6} \mathrm{H}_{6}\right),(\mathrm{b}) \mathrm{CH}_{3} \mathrm{Cl},(\mathrm{c}) \mathrm{PF}_{3},(\mathrm{d}) \mathrm{NaCl},(\mathrm{e}) \mathrm{CS}_{2}$.

Shazia Naz

Numerade Educator

Problem 12

Ammonia is both a donor and an acceptor of hydrogen in hydrogen-bond formation. Draw a diagram showing the hydrogen bonding of an ammonia molecule with two other ammonia molecules.

Kyle Gassaway

Numerade Educator

Problem 13

Arrange the following in order of increasing boiling point: RbF, $\mathrm{CO}_{2}, \mathrm{CH}_{3} \mathrm{OH}, \mathrm{CH}_{3} \mathrm{Br} .$ Explain your reasoning.

Kyle Gassaway

Numerade Educator

Problem 14

Arrange the following in order of increasing boiling point: RbF, $\mathrm{CO}_{2}, \mathrm{CH}_{3} \mathrm{OH}, \mathrm{CH}_{3} \mathrm{Br} .$ Explain your reasoning.

Kyle Gassaway

Numerade Educator

Problem 15

Diethyl ether has a boiling point of $34.5^{\circ} \mathrm{C}$, and 1 -butanol has a boiling point of $117^{\circ} \mathrm{C}$ :
Both of these compounds have the same numbers and types of atoms. Explain the difference in their boiling points.

David Collins

Numerade Educator

Problem 16

Which member of each of the following pairs of substances would you expect to have a higher boiling point: (a) $\mathrm{O}_{2}$ and $\mathrm{Cl}_{2}$ (b) $\mathrm{SO}_{2}$ and $\mathrm{CO}_{2},$ (c) HF and HI?

Kyle Gassaway

Numerade Educator

Problem 17

Which substance in each of the following pairs would you expect to have the higher boiling point: (a) Ne or Xe, (b) $\mathrm{CO}_{2}$ or $\mathrm{CS}_{2}$, (c) $\mathrm{CH}_{4}$ or $\mathrm{Cl}_{2},$ (d) $\mathrm{F}_{2}$ or LiF, (e) $\mathrm{NH}_{3}$ or $\mathrm{PH}_{3}$ ? Explain why.

Jake Rempel

Numerade Educator

Problem 18

Explain in terms of intermolecular forces why (a) $\mathrm{NH}_{3}$ has a higher boiling point than $\mathrm{CH}_{4}$ and (b) KCl has a higher melting point than $\mathrm{I}_{2}$.

Kyle Gassaway

Numerade Educator

Problem 19

What kind of attractive forces must be overcome to (a) melt ice, (b) boil molecular bromine, (c) melt solid iodine, and (d) dissociate $\mathrm{F}_{2}$ into $\mathrm{F}$ atoms?

Shazia Naz

Numerade Educator

Problem 20

The following compounds have the same molecular formulas $\left(\mathrm{C}_{4} \mathrm{H}_{10}\right) .$ Which one would you expect to have a higher boiling point?

Kyle Gassaway

Numerade Educator

Problem 21

Explain the difference in the melting points of the following compounds:
(Hint: One of the two can form intramolecular hydrogen bonds.)

Jake Rempel

Numerade Educator

Problem 22

Explain why liquids, unlike gases, are virtually incompressible.

Kyle Gassaway

Numerade Educator

Problem 23

What is surface tension? What is the relationship between intermolecular forces and surface tension? How does surface tension change with temperature?

Jake Rempel

Numerade Educator

Problem 24

Despite the fact that stainless steel is much denser than water, a stainless-steel razor blade can be made to float on water. Why?

Kyle Gassaway

Numerade Educator

Problem 25

Use water and mercury as examples to explain adhesion and cohesion.

Jake Rempel

Numerade Educator

Problem 26

A glass can be filled slightly above the rim with water. Explain why the water does not overflow.

Kyle Gassaway

Numerade Educator

Problem 27

Draw diagrams showing the capillary action of (a) water and (b) mercury in three tubes of different radii.

Jake Rempel

Numerade Educator

Problem 28

What is viscosity? What is the relationship between intermolecular forces and viscosity?

Kyle Gassaway

Numerade Educator

Problem 29

Why does the viscosity of a liquid decrease with increasing temperature?

Jake Rempel

Numerade Educator

Problem 30

Why is ice less dense than water?

Kyle Gassaway

Numerade Educator

Problem 31

Outdoor water pipes have to be drained or insulated in winter in a cold climate. Why?

Jake Rempel

Numerade Educator

Problem 32

Predict which of the following liquids has greater surface tension:
ethanol $\left(\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}\right)$ or dimethyl ether $\left(\mathrm{CH}_{3} \mathrm{OCH}_{3}\right)$.

Kyle Gassaway

Numerade Educator

Problem 33

Predict the viscosity of ethylene glycol relative to that of ethanol and glycerol (see Table 12.3).
$$\begin{array}{l}\mathrm{CH}_{2}-\mathrm{OH} \\\mathrm{CH}_{2}-\mathrm{OH}\end{array}$$ Ethylene glycol

Shazia Naz

Numerade Educator

Problem 34

Define the following terms: crystalline solid, lattice point, unit cell, coordination number, closest packing.

Kyle Gassaway

Numerade Educator

Problem 35

Describe the geometries of the following cubic cells: simple cubic, body-centered cubic, face-centered cubic. Which of these structures would give the highest density for the same type of atoms? Which the lowest?

Jake Rempel

Numerade Educator

Problem 36

Classify the solid states in terms of crystal types of the elements in the third period of the periodic table. Predict the trends in their melting points and boiling points.

Kyle Gassaway

Numerade Educator

Problem 37

The melting points of the oxides of the third-period elements are given in parentheses: $\mathrm{Na}_{2} \mathrm{O}\left(1275^{\circ} \mathrm{C}\right), \mathrm{MgO}\left(2800^{\circ} \mathrm{C}\right), \mathrm{Al}_{2} \mathrm{O}_{3}$ $\left(2045^{\circ} \mathrm{C}\right), \mathrm{SiO}_{2}\left(1610^{\circ} \mathrm{C}\right), \mathrm{P}_{4} \mathrm{O}_{10}\left(580^{\circ} \mathrm{C}\right), \mathrm{SO}_{3}\left(16.8^{\circ} \mathrm{C}\right), \mathrm{Cl}_{2} \mathrm{O}_{7}$
$\left(-91.5^{\circ} \mathrm{C}\right) .$ Classify these solids in terms of crystal types.

Jake Rempel

Numerade Educator

Problem 38

Define X-ray diffraction. What are the typical wavelengths (in nm) of X rays (see Figure 6.1 ).

Shazia Naz

Numerade Educator

Problem 39

Write the Bragg equation. Define every term and describe how this equation can be used to measure interatomic distances.

Jake Rempel

Numerade Educator

Problem 40

What is the coordination number of each sphere in (a) a simple cubic cell, (b) a body-centered cubic cell, and (c) a face-centered cubic cell? Assume the spheres are all the same.

Kyle Gassaway

Numerade Educator

Problem 41

Calculate the number of spheres that would be found within a simple cubic cell, body-centered cubic cell, and face-centered cubic cell. Assume that the spheres are the same.

Jake Rempel

Numerade Educator

Problem 42

Metallic iron crystallizes in a cubic lattice. The unit cell edge length is $287 \mathrm{pm}$. The density of iron is $7.87 \mathrm{g} / \mathrm{cm}^{3}$. How many iron atoms are within a unit cell?

Kyle Gassaway

Numerade Educator

Problem 43

Barium metal crystallizes in a body-centered cubic lattice (the Ba atoms are at the lattice points only). The unit cell edge length is $502 \mathrm{pm}$, and the density of the metal is $3.50 \mathrm{g} / \mathrm{cm}^{3}$. Using this information, calculate Avogadro's number. [Hint: First calculate the volume (in $\mathrm{cm}^{3}$ ) occupied by 1 mole of Ba atoms in the unit cells. Next calculate the volume (in $\mathrm{cm}^{3}$ ) occupied by one $\mathrm{Ba}$ atom in the unit cell. Assume that 68 percent of the unit cell is occupied by Ba atoms.]

Shazia Naz

Numerade Educator

Problem 44

Vanadium crystallizes in a body-centered cubic lattice (the $\mathrm{V}$ atoms occupy only the lattice points). How many $\mathrm{V}$ atoms are present in a unit cell?

Kyle Gassaway

Numerade Educator

Problem 45

Europium crystallizes in a body-centered cubic lattice (the Eu atoms occupy only the lattice points). The density of Eu is $5.26 \mathrm{g} / \mathrm{cm}^{3} .$ Calculate the unit cell edge length in picometers.

Shazia Naz

Numerade Educator

Problem 46

Crystalline silicon has a cubic structure. The unit cell edge length is $543 \mathrm{pm} .$ The density of the solid is $2.33 \mathrm{g} / \mathrm{cm}^{3}$. Calculate the number of Si atoms in one unit cell.

Kyle Gassaway

Numerade Educator

Problem 47

A face-centered cubic cell contains $8 \mathrm{X}$ atoms at the corners of the cell and $6 \mathrm{Y}$ atoms at the faces. What is the empirical formula of the solid?

Banhishikha Sinha

Banhishikha Sinha

Numerade Educator

Problem 48

When $X$ rays of wavelength 0.090 nm are diffracted by a metallic crystal, the angle of first-order diffraction $(n=1)$ is measured to be $15.2^{\circ} .$ What is the distance (in $\mathrm{pm}$ ) between the layers of atoms responsible for the diffraction?

Kyle Gassaway

Numerade Educator

Problem 49

The distance between layers in an $\mathrm{NaCl}$ crystal is $282 \mathrm{pm} . \mathrm{X}$ rays are diffracted from these layers at an angle of $23.0^{\circ}$. Assuming that $n=1,$ calculate the wavelength of the $X$ rays in nanometers.

Shazia Naz

Numerade Educator

Problem 50

Identify the unit cell of molecular iodine $\left(\mathrm{I}_{2}\right)$ shown here. (Hint:
Consider the position of iodine molecules, not individual iodine atoms.)

David Collins

Numerade Educator

Problem 51

Shown here is a zinc oxide unit cell. What is the formula of zinc oxide?

Shazia Naz

Numerade Educator

Problem 52

Describe and give examples of the following types of crystals:
(a) ionic crystals, (b) covalent crystals, (c) molecular crystals,
(d) metallic crystals.

Kyle Gassaway

Numerade Educator

Problem 53

Why are metals good conductors of heat and electricity? Why does the ability of a metal to conduct electricity decrease with increasing temperature?

Jake Rempel

Numerade Educator

Problem 54

A solid is hard, brittle, and electrically nonconducting. Its melt (the liquid form of the substance) and an aqueous solution containing the substance conduct electricity. Classify the solid.

Ronald Prasad

Numerade Educator

Problem 55

A solid is soft and has a low melting point (below $100^{\circ} \mathrm{C}$ ). The solid, its melt, and an aqueous solution containing the substance are all nonconductors of electricity. Classify the solid.

Jake Rempel

Numerade Educator

Problem 56

A solid is very hard and has a high melting point. Neither the solid nor its melt conducts electricity. Classify the solid.

Kyle Gassaway

Numerade Educator

Problem 57

Which of the following are molecular solids and which are covalent solids: $\mathrm{Se}_{8}, \mathrm{HBr}, \mathrm{Si}, \mathrm{CO}_{2}, \mathrm{C}, \mathrm{P}_{4} \mathrm{O}_{6}, \mathrm{SiH}_{4} ?$

Shazia Naz

Numerade Educator

Problem 58

Classify the solid state of the following substances as ionic crystals, covalent crystals, molecular crystals, or metallic crystals: (a) $\mathrm{CO}_{2},$ (b) $\mathrm{B}_{12},$ (c) $\mathrm{S}_{8},$ (d) $\mathrm{KBr},$ (e) $\mathrm{Mg},$ (f) $\mathrm{SiO}_{2},$ (g) LiCl, (h) Cr.

Kyle Gassaway

Numerade Educator

Problem 59

Explain why diamond is harder than graphite. Why is graphite an electrical conductor but diamond is not?

Jake Rempel

Numerade Educator

Problem 60

What is an amorphous solid? How does it differ from a crystalline solid?

Kyle Gassaway

Numerade Educator

Problem 61

Define glass. What is the chief component of glass? Name three types of glass.

Noah Barguez-Arias

Noah Barguez-Arias

Numerade Educator

Problem 62

What is a phase change? Name all possible changes that can occur among the vapor, liquid, and solid phases of a substance.

Kyle Gassaway

Numerade Educator

Problem 63

What is the equilibrium vapor pressure of a liquid? How is it measured, and how does it change with temperature?

Jake Rempel

Numerade Educator

Problem 64

Use any one of the phase changes to explain what is meant by dynamic equilibrium.

Kyle Gassaway

Numerade Educator

Problem 65

Define the following terms: (a) molar heat of vaporization, (b) molar heat of fusion, (c) molar heat of sublimation. What are their typical units?

Shazia Naz

Numerade Educator

Problem 66

How is the molar heat of sublimation related to the molar heats of vaporization and fusion? On what law are these relationships based?

Kyle Gassaway

Numerade Educator

Problem 67

What can we learn about the intermolecular forces in a liquid from the molar heat of vaporization?

Jake Rempel

Numerade Educator

Problem 68

The greater the molar heat of vaporization of a liquid, the greater its vapor pressure. True or false?

Kyle Gassaway

Numerade Educator

Problem 69

Define boiling point. How does the boiling point of a liquid depend on external pressure? Referring to Table $11.5,$ what is the boiling point of water when the external pressure is $187.5 \mathrm{mmHg} ?$

Shazia Naz

Numerade Educator

Problem 70

As a liquid is heated at constant pressure, its temperature rises. This trend continues until the boiling point of the liquid is reached. No further rise in temperature of the liquid can be induced by heating. Explain.

Kyle Gassaway

Numerade Educator

Problem 71

What is critical temperature? What is the significance of critical temperature in condensation of gases?

Shazia Naz

Numerade Educator

Problem 72

What is the relationship between intermolecular forces in a liquid and the liquid's boiling point and critical temperature? Why is the critical temperature of water greater than that of most other substances?

Kyle Gassaway

Numerade Educator

Problem 73

How do the boiling points and melting points of water and carbon tetrachloride vary with pressure? Explain any difference in behavior of these two substances.

Jake Rempel

Numerade Educator

Problem 74

Why is solid carbon dioxide called dry ice?

Kyle Gassaway

Numerade Educator

Problem 75

The vapor pressure of a liquid in a closed container depends on which of the following: (a) the volume above the liquid, (b) the amount of liquid present, (c) temperature, (d) intermolecular forces between the molecules in the liquid?

Jake Rempel

Numerade Educator

Problem 76

Wet clothes dry more quickly on a hot, dry day than on a hot, humid day. Explain.

Jake Rempel

Numerade Educator

Problem 77

Which of the following phase transitions gives off more heat:
(a) 1 mole of steam to 1 mole of water at $100^{\circ} \mathrm{C}$, or (b) 1 mole of water to 1 mole of ice at $0^{\circ} \mathrm{C}$ ?

Kyle Gassaway

Numerade Educator

Problem 78

A beaker of water is heated to boiling by a Bunsen burner. Would adding another burner raise the temperature of the boiling water? Explain.

Shazia Naz

Numerade Educator

Problem 79

Explain why splashing a small amount of liquid nitrogen (b.p. 77 K) is not as harmful as splashing boiling water on your skin.

Jake Rempel

Numerade Educator

Problem 80

Calculate the amount of heat (in $\mathrm{kJ}$ ) required to convert $150.2 \mathrm{g}$ of water to steam at $100^{\circ} \mathrm{C}$.

David Collins

Numerade Educator

Problem 81

How much heat (in $\mathrm{kJ}$ ) is needed to convert $866 \mathrm{g}$ of ice at $-15^{\circ} \mathrm{C}$ to steam at $146^{\circ} \mathrm{C} ?$ (The specific heats of ice and steam are 2.03 and $1.99 \mathrm{J} / \mathrm{g} \cdot^{\circ} \mathrm{C}$, respectively.)

David Collins

Numerade Educator

Problem 82

How is the rate of evaporation of a liquid affected by (a) temperature, (b) the surface area of a liquid exposed to air, (c) intermolecular forces?

Kyle Gassaway

Numerade Educator

Problem 83

The molar heats of fusion and sublimation of molecular iodine are 15.27 and $62.30 \mathrm{kJ} / \mathrm{mol}$, respectively. Estimate the molar heat of vaporization of liquid iodine.

Jake Rempel

Numerade Educator

Problem 84

The following compounds, listed with their boiling points, are liquid at $-10^{\circ} \mathrm{C}:$ butane, $-0.5^{\circ} \mathrm{C} ;$ ethanol, $78.3^{\circ} \mathrm{C} ;$ toluene, $110.6^{\circ} \mathrm{C} . \mathrm{At}-10^{\circ} \mathrm{C},$ which of these liquids would you expect to have the highest vapor pressure? Which the lowest? Explain.

Ronald Prasad

Numerade Educator

Problem 85

Freeze-dried coffee is prepared by freezing brewed coffee and then removing the ice component with a vacuum pump. Describe the phase changes taking place during these processes.

Jake Rempel

Numerade Educator

Problem 86

A student hangs wet clothes outdoors on a winter day when the temperature is $-15^{\circ} \mathrm{C}$. After a few hours, the clothes are found to be fairly dry. Describe the phase changes in this drying process.

Kyle Gassaway

Numerade Educator

Problem 87

Explain why steam at $100^{\circ} \mathrm{C}$ causes more serious burns than water at $100^{\circ} \mathrm{C}$.

Shazia Naz

Numerade Educator

Problem 88

Vapor pressure measurements at several different temperatures are shown for mercury. Determine graphically the molar heat of vaporization for mercury.
$$\begin{array}{lcclll}T\left(^{\circ} \mathrm{C}\right) & 200 & 250 & 300 & 320 & 340 \\\hline P(\mathrm{mmHg}) & 17.3 & 74.4 & 246.8 & 376.3 & 557.9\end{array}$$

Alexander Cheng

Alexander Cheng

Numerade Educator

Problem 89

The vapor pressure of benzene $\left(\mathrm{C}_{6} \mathrm{H}_{6}\right)$ is $40.1 \mathrm{mm} \mathrm{Hg}$ at $7.6^{\circ} \mathrm{C}$. What is its vapor pressure at $60.6^{\circ} \mathrm{C} ?$ The molar heat of vaporization of benzene is $31.0 \mathrm{kJ} / \mathrm{mol}$.

Jake Rempel

Numerade Educator

Problem 90

The vapor pressure of liquid $X$ is lower than that of liquid $Y$ at $20^{\circ} \mathrm{C},$ but higher at $60^{\circ} \mathrm{C} .$ What can you deduce about the relative magnitude of the molar heats of vaporization of $X$ and $Y$ ?

Prashant Bana

Numerade Educator

Problem 91

Estimate the molar heat of vaporization of a liquid whose vapor pressure doubles when the temperature is raised from $85^{\circ} \mathrm{C}$ to $95^{\circ} \mathrm{C}$.

Kyle Gassaway

Numerade Educator

Problem 92

What is a phase diagram? What useful information can be obtained from studying a phase diagram?

Shazia Naz

Numerade Educator

Problem 93

Explain how water's phase diagram differs from those of most substances. What property of water causes the difference?

Jake Rempel

Numerade Educator

Problem 94

The blades of ice skates are quite thin, so the pressure exerted on ice by a skater can be substantial. Explain how this facilitates skating on ice.

Shazia Naz

Numerade Educator

Problem 95

A length of wire is placed on top of a block of ice. The ends of the wire extend over the edges of the ice, and a heavy weight is attached to each end. It is found that the ice under the wire gradually melts, so the wire slowly moves through the ice block. At the same time, the water above the wire refreezes. Explain the phase changes that accompany this phenomenon.

Jake Rempel

Numerade Educator

Problem 96

The boiling point and freezing point of sulfur dioxide are $-10^{\circ} \mathrm{C}$ and $-72.7^{\circ} \mathrm{C}$ (at 1 atm), respectively. The triple point is $-75.5^{\circ} \mathrm{C}$ and $1.65 \times 10^{-3}$ atm, and its critical point is at $157^{\circ} \mathrm{C}$ and 78 atm. On the basis of this information, draw a rough sketch of the phase diagram of $\mathrm{SO}_{2}$.

Kyle Gassaway

Numerade Educator

Problem 97

A phase diagram of water is shown. Label the regions. Predict what would happen as a result of the following changes:
(a) Starting at $\mathrm{A},$ we raise the temperature at constant pressure.
(b) Starting at $\mathrm{B}$, we lower the pressure at constant temperature.
(c) Starting at $\mathrm{C}$, we lower the temperature at constant pressure.

Shazia Naz

Numerade Educator

Problem 98

Name the kinds of attractive forces that must be overcome in order to (a) boil liquid ammonia, (b) melt solid phosphorus ( $\mathrm{P}_{4}$ ), (c) dissolve CsI in liquid HF, (d) melt potassium metal.

Kyle Gassaway

Numerade Educator

Problem 99

Which of the following properties indicates very strong intermolecular forces in a liquid: (a) very low surface tension, (b) very low critical temperature, (c) very low boiling point, (d) very low vapor pressure?

Jake Rempel

Numerade Educator

Problem 100

At $-35^{\circ} \mathrm{C},$ liquid $\mathrm{HI}$ has a higher vapor pressure than liquid $\mathrm{HF}$. Explain.

Sandra Lundell

Numerade Educator

Problem 101

Based on the following properties of elemental boron, classify it as one of the crystalline solids discussed in Section 12.4: high melting point $\left(2300^{\circ} \mathrm{C}\right),$ poor conductor of heat and electricity, insoluble in water, very hard substance.

Shazia Naz

Numerade Educator

Problem 102

Referring to Figure $12.34,$ determine the stable phase of $\mathrm{CO}_{2}$ at
(a) 4 atm and $-60^{\circ} \mathrm{C}$ and (b) 0.5 atm and $-20^{\circ} \mathrm{C}$.

Kyle Gassaway

Numerade Educator

Problem 103

Which of the following substances has the highest polarizability:
$\mathrm{CH}_{4}, \mathrm{H}_{2}, \mathrm{CCl}_{4}, \mathrm{SF}_{6}, \mathrm{H}_{2} \mathrm{S} ?$

Shazia Naz

Numerade Educator

Problem 104

Given two complementary strands of DNA containing 100 base pairs each, calculate the ratio of two separate strands to hydrogen-bonded double helix in solution at $300 \mathrm{K}$. (Hint: The formula for calculating this ratio is $e^{-\Delta E R T},$ where $\Delta E$ is the energy difference between hydrogen-bonded double-strand DNAs and single-strand DNAs and $R$ is the gas constant.) Assume the energy of hydrogen bonds per base pair to be $10 \mathrm{kJ} / \mathrm{mol}$.

David Collins

Numerade Educator

Problem 105

The average distance between base pairs measured parallel to the axis of a DNA molecule is 3.4 A. The average molar mass of a pair of nucleotides is $650 \mathrm{g} / \mathrm{mol} .$ Estimate the length in centimeters of a DNA molecule of molar mass $5.0 \times 10^{9} \mathrm{g} / \mathrm{mol}$ Roughly how many base pairs are contained in this molecule?

Shazia Naz

Numerade Educator

Problem 106

A $\mathrm{CO}_{2}$ fire extinguisher is located on the outside of a building in Massachusetts. During the winter months, one can hear a sloshing sound when the extinguisher is gently shaken. In the summertime there is often no sound when it is shaken. Explain. Assume that the extinguisher has no leaks and that it has not been used.

Shazia Naz

Numerade Educator

Problem 107

What is the vapor pressure of mercury at its normal boiling point $\left(357^{\circ} \mathrm{C}\right) ?$

Jake Rempel

Numerade Educator

Problem 108

A flask of water is connected to a powerful vacuum pump. When the pump is turned on, the water begins to boil. After a few minutes, the same water begins to freeze. Eventually, the ice disappears. Explain what happens at each step.

Kyle Gassaway

Numerade Educator

Problem 109

The liquid-vapor boundary line in the phase diagram of any substance always stops abruptly at a certain point. Why?

Ronald Prasad

Numerade Educator

Problem 110

The interionic distance of several alkali halide crystals are as follows:
$$\begin{array}{lllllll}\text { Crystal } & \mathrm{NaCl} & \mathrm{NaBr} & \mathrm{NaI} & \mathrm{KCl} & \mathrm{KBr} & \mathrm{KI} \\\hline \text { Interionic } & 282 & 299 & 324 & 315 & 330 & 353\end{array}$$
distance (pm)
Plot lattice energy versus the reciprocal interionic distance. How would you explain the plot in terms of the dependence of lattice energy on the distance of separation between ions? What law governs this interaction? (For lattice energies, see Table $8.1 .$ )

David Collins

Numerade Educator

Problem 111

Which has a greater density, crystalline $\mathrm{SiO}_{2}$ or amorphous $\mathrm{SiO}_{2} ?$ Why?

Jake Rempel

Numerade Educator

Problem 112

A student is given four solid samples labeled $\mathrm{W}, \mathrm{X}, \mathrm{Y},$ and $\mathrm{Z}$ All have a metallic luster. She is told that the solids could be gold, lead sulfide, mica (which is quartz, or $\mathrm{SiO}_{2}$ ), and iodine. The results of her investigations are: (a) $\mathrm{W}$ is a good electrical conductor; X, Y, and Z are poor electrical conductors. (b) When the solids are hit with a hammer, W flattens out, X shatters into many pieces, Y is smashed into a powder, and Z is not affected.
(c) When the solids are heated with a Bunsen burner, Y melts with some sublimation, but $X, W,$ and $Z$ do not melt. (d) In treatment with $6 M \mathrm{HNO}_{3}, \mathrm{X}$ dissolves; there is no effect on $\mathrm{W}, \mathrm{Y}$ or $\mathrm{Z.}$ On the basis of these test results, identify the solids.

Shazia Naz

Numerade Educator

Problem 113

Which of the following statements are false? (a) Dipole-dipole interactions between molecules are greatest if the molecules possess only temporary dipole moments. (b) All compounds containing hydrogen atoms can participate in hydrogen-bond formation. (c) Dispersion forces exist between all atoms, molecules, and ions.

Shazia Naz

Numerade Educator

Problem 114

The diagram shows a kettle of boiling water on a stove. Identify the phases in regions $A$ and $B$.

Kyle Gassaway

Numerade Educator

Problem 115

The south pole of Mars is covered with solid carbon dioxide, which partly sublimes during the summer. The $\mathrm{CO}_{2}$ vapor recondenses in the winter when the temperature drops to 150
K. Given that the heat of sublimation of $\mathrm{CO}_{2}$ is $25.9 \mathrm{kJ} / \mathrm{mol}$, calculate the atmospheric pressure on the surface of Mars. [Hint: Use Figure 12.34 to determine the normal sublimation temperature of dry ice and Equation 12.4 which also applies to sublimations.]

Shazia Naz

Numerade Educator

Problem 116

The properties of gases, liquids, and solids differ in a number of respects. How would you use the kinetic molecular theory (see Section 11.6 ) to explain the following observations? (a) Ease of compressibility decreases from gas to liquid to solid. (b) Solids retain a definite shape, but gases and liquids do not. (c) For most substances, the volume of a given amount of material increases as it changes from solid to liquid to gas.

David Collins

Numerade Educator

Problem 117

Select the substance in each pair that should have the higher boiling point. In each case identify the principal intermolecular forces involved and account briefly for your choice: (a) $\mathrm{K}_{2} \mathrm{S}$ or $\left(\mathrm{CH}_{3}\right)_{3} \mathrm{N},(\mathrm{b}) \mathrm{Br}_{2}$ or $\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{3}$.

Jake Rempel

Numerade Educator

Problem 118

A small drop of oil in water assumes a spherical shape. Explain. (Hint: Oil is made up of nonpolar molecules, which tend to avoid contact with water.)

Kyle Gassaway

Numerade Educator

Problem 119

Under the same conditions of temperature and density, which of the following gases would you expect to behave less ideally: $\mathrm{CH}_{4}$ or $\mathrm{SO}_{2} ?$ Explain.

Jake Rempel

Numerade Educator

Problem 120

The fluorides of the second-period elements and their melting points are: LiF, $845^{\circ} \mathrm{C} ; \mathrm{BeF}_{2}, 800^{\circ} \mathrm{C} ; \mathrm{BF}_{3},-126.7^{\circ} \mathrm{C} ; \mathrm{CF}_{4},$
$-184^{\circ} \mathrm{C} ; \mathrm{NF}_{3},-206.6^{\circ} \mathrm{C} ; \mathrm{OF}_{2},-223.8^{\circ} \mathrm{C} ; \mathrm{F}_{2},-219.6^{\circ} \mathrm{C}$.
Classify the type(s) of intermolecular forces present in each compound.

Shazia Naz

Numerade Educator

Problem 121

The standard enthalpy of formation of gaseous molecular iodine is $62.4 \mathrm{kJ} / \mathrm{mol} .$ Use this information to calculate the molar heat of sublimation of molecular iodine at $25^{\circ} \mathrm{C}$.

Vishal Sharma

Numerade Educator

Problem 122

The distance between $L i^{+}$ and $C l^{-}$ is 257 pm in solid LiCl and $203 \mathrm{pm}$ in an LiCl unit in the gas phase. Explain the difference in the bond lengths.

Kyle Gassaway

Numerade Educator

Problem 123

Heat of hydration, that is, the heat change that occurs when ions become hydrated in solution, is largely due to ion-dipole interactions. The heats of hydration for the alkali metal ions are $\mathrm{Li}^{+},-520 \mathrm{kJ} / \mathrm{mol} ; \mathrm{Na}^{+},-405 \mathrm{kJ} / \mathrm{mol} ; \mathrm{K}^{+},-321 \mathrm{kJ} / \mathrm{mol}$. Account for the trend in these values.

Shazia Naz

Numerade Educator

Problem 124

If water were a linear molecule, (a) would it still be polar, and
(b) would the water molecules still be able to form hydrogen bonds with one another?

Kyle Gassaway

Numerade Educator

Problem 125

Calculate the $\Delta H^{\circ}$ for the following processes at $25^{\circ} \mathrm{C}$ :
(a) $\mathrm{Br}_{2}(l) \longrightarrow \mathrm{Br}_{2}(g)$ and $(\mathrm{b}) \mathrm{Br}_{2}(g) \longrightarrow 2 \mathrm{Br}(g) .$ Comment on the relative magnitudes of these $\Delta H^{\circ}$ values in terms of the forces involved in each case. (Hint: See Table 8.6.)

David Collins

Numerade Educator

Problem 126

Which liquid would you expect to have a greater viscosity, water or diethyl ether? The structure of diethyl ether is shown in Problem 12.15.

Shazia Naz

Numerade Educator

Problem 127

A beaker of water is placed in a closed container. Predict the effect on the vapor pressure of the water when (a) its temperature is lowered, (b) the volume of the container is doubled, (c) more water is added to the beaker.

Dr. Satish Ingale

Dr. Satish Ingale

Numerade Educator

Problem 128

Ozone $\left(\mathrm{O}_{3}\right)$ is a strong oxidizing agent that can oxidize all the common metals except gold and platinum. A convenient test for ozone is based on its action on mercury. When exposed to ozone, mercury becomes dull looking and sticks to glass tubing (instead of flowing freely through it). Write a balanced equation for the reaction. What property of mercury is altered by its interaction with ozone?

Kyle Gassaway

Numerade Educator

Problem 129

A sample of limestone $\left(\mathrm{CaCO}_{3}\right)$ is heated in a closed vessel until it is partially decomposed. Write an equation for the reaction, and state how many phases are present.

Shazia Naz

Numerade Educator

Problem 130

Carbon and silicon belong to Group $4 \mathrm{A}$ of the periodic table and have the same valence electron configuration $\left(n s^{2} n p^{2}\right) .$ Why does silicon dioxide $\left(\mathrm{SiO}_{2}\right)$ have a much higher melting point than carbon dioxide $\left(\mathrm{CO}_{2}\right) ?$

Shazia Naz

Numerade Educator

Problem 131

Gaseous or highly volatile liquid anesthetics are often preferred in surgical procedures because once inhaled, these vapors can quickly enter the bloodstream through the alveoli and then enter the brain. Several common gaseous anesthetics are shown with their boiling points:
Based on intermolecular force considerations, explain the advantages of using these anesthetics. (Hint: The brain barrier is made of membranes that have a nonpolar interior region.)

Kyle Gassaway

Numerade Educator

Problem 132

Given the general properties of water and ammonia, comment on the problems that a biological system (as we know it) would have developing in an ammonia medium.
$$\begin{array}{lll}
\text { Boiling point } & \mathrm{H}_{2} \mathrm{O} & \mathrm{NH}_{3} \\
\text { Melting point } & 373.15 \mathrm{K} & 239.65 \mathrm{K} \\
\text { Molar heat capacity } & 273.15 \mathrm{K} & 195.3 \mathrm{K} \\
\text { Molar heat of vaporization } & 45.3 \mathrm{J} / \mathrm{K} \cdot \mathrm{mol} & 8.53 \mathrm{J} / \mathrm{K} \cdot \mathrm{mol} \\
\text { Molar heat of fusion } & 40.79 \mathrm{kJ} / \mathrm{mol} & 23.3 \mathrm{kJ} / \mathrm{mol} \\\text { Viscosity } & 0.001 \mathrm{N} \cdot \mathrm{s} / \mathrm{m}^{2} & 0.0254 \mathrm{N} \cdot \mathrm{s} / \mathrm{m}^{2} \\
& & (\text { at } 240 \mathrm{K}) \\
\text { Dipole moment } & 1.82 \mathrm{D} & 1.46 \mathrm{D} \\
\text { Phase at } 300 \mathrm{K} & \text { Liquid } & \text { Gas }
\end{array}$$

David Collins

Numerade Educator

Problem 133

A pressure cooker is a sealed container that allows steam to escape when it exceeds a predetermined pressure. How does this device reduce the time needed for cooking?

Kyle Gassaway

Numerade Educator

Problem 134

A 1.20 -g sample of water is injected into an evacuated $5.00-\mathrm{L}$ flask at $65^{\circ} \mathrm{C}$. What percentage of the water will be vapor when the system reaches equilibrium? Assume ideal behavior of water vapor and that the volume of liquid water is negligible. The vapor pressure of water at $65^{\circ} \mathrm{C}$ is $187.5 \mathrm{mmHg}$.

Shazia Naz

Numerade Educator

Problem 135

What are the advantages of cooking the vegetable broccoli with steam instead of boiling it in water?

Kyle Gassaway

Numerade Educator

Problem 136

A quantitative measure of how efficiently spheres pack into unit cells is called packing efficiency, which is the percentage of the cell space occupied by the spheres. Calculate the packing efficiencies of a simple cubic cell, a body-centered cubic cell, and a face-centered cubic cell. (Hint: Refer to Figure 12.24 and use the relationship that the volume of a sphere is $\frac{4}{3} \pi r^{3},$ where $r$ is the radius of the sphere.)

Jake Rempel

Numerade Educator

Problem 137

The phase diagram of helium is shown. Helium is the only known substance that has two different liquid phases: helium-I and helium-II. (a) What is the maximum temperature at which helium-II can exist? (b) What is the minimum pressure at which solid helium can exist? (c) What is the normal boiling point of helium-I? (d) Can solid helium sublime?

Shazia Naz

Numerade Educator

Problem 138

The phase diagram of sulfur is shown. (a) How many triple points are there? (b) Which is the more stable allotrope under ordinary atmospheric conditions? (c) Describe what happens when sulfur at 1 atm is heated from $80^{\circ} \mathrm{C}$ to $200^{\circ} \mathrm{C}$.

Shazia Naz

Numerade Educator

Problem 139

Provide an explanation for each of the following phenomena: (a) Solid argon (m.p. $-189.2^{\circ} \mathrm{C} ;$ b.p. $-185.7^{\circ} \mathrm{C}$ ) can be prepared by immersing a flask containing argon gas in liquid nitrogen (b.p. $-195.8^{\circ} \mathrm{C}$ ) until it liquefies and then connecting the flask to a vacuum pump. (b) The melting point of cyclohexane $\left(C_{6} H_{12}\right)$ increases with increasing pressure exerted on the solid cyclohexane. (c) Certain high-altitude clouds contain water droplets at $-10^{\circ} \mathrm{C}$. (d) When a piece of dry ice is added to a beaker of water, fog forms above the water.

Kyle Gassaway

Numerade Educator

Problem 140

Argon crystallizes in the face-centered cubic arrangement at 40 K. Given that the atomic radius of argon is $191 \mathrm{pm},$ calculate the density of solid argon.

Jake Rempel

Numerade Educator

Problem 141

Given the phase diagram of carbon, answer the following questions: (a) How many triple points are there and what are the phases that can coexist at each triple point? (b) Which has a higher density, graphite or diamond? (c) Synthetic diamond can be made from graphite. Using the phase diagram, how would you go about making diamond?

Shazia Naz

Numerade Educator

Problem 142

A chemistry instructor performed the following mystery demonstration. Just before the students arrived in class, she heated some water to boiling in an Erlenmeyer flask. She then removed the flask from the flame and closed the flask with a rubber stopper. After the class commenced, she held the flask in front of the students and announced that she could make the water boil simply by rubbing an ice cube on the outside walls of the flask. To the amazement of everyone, it worked. Give an explanation for this phenomenon.

Kyle Gassaway

Numerade Educator

Problem 143

Swimming coaches sometimes suggest that a drop of alcohol (ethanol) placed in an ear plugged with water "draws out the water." Explain this action from a molecular point of view.

Kyle Gassaway

Numerade Educator

Problem 144

Use the concept of intermolecular forces to explain why the far end of a walking cane rises when one raises the handle.

Jake Rempel

Numerade Educator

Problem 145

Why do citrus growers spray their trees with water to protect them from freezing?

Kyle Gassaway

Numerade Educator

Problem 146

What is the origin of dark spots on the inner glass walls of an old tungsten lightbulb? What is the purpose of filling these light-bulbs with argon gas?

Shazia Naz

Numerade Educator

Problem 147

A student heated a beaker of cold water (on a tripod) with a Bunsen burner. When the gas was ignited, she noticed that there was water condensed on the outside of the beaker. Explain what happened.

Shazia Naz

Numerade Educator

Problem 148

The compound dichlorodifluoromethane $\left(\mathrm{CCl}_{2} \mathrm{F}_{2}\right)$ has a normal boiling point of $-30^{\circ} \mathrm{C},$ a critical temperature of $112^{\circ} \mathrm{C}$ and a corresponding critical pressure of 40 atm. If the gas is compressed to 18 atm at $20^{\circ} \mathrm{C},$ will the gas condense? Your answer should be based on a graphical interpretation.

Kyle Gassaway

Numerade Educator

Problem 149

Iron crystallizes in a body-centered cubic lattice. The cell length as determined by X-ray diffraction is $286.7 \mathrm{pm}$. Given that the density of iron is $7.874 \mathrm{g} / \mathrm{cm}^{3},$ calculate Avogadro's number.

Shazia Naz

Numerade Educator

Problem 150

Sketch the cooling curves of water from about $110^{\circ} \mathrm{C}$ to about $-10^{\circ} \mathrm{C} .$ How would you also show the formation of supercooled liquid below $0^{\circ} \mathrm{C}$ which then freezes to ice? The pressure is at $1 \mathrm{atm}$ throughout the process. The curves need not be drawn quantitatively.

Kyle Gassaway

Numerade Educator

Problem 151

The boiling point of methanol is $65.0^{\circ} \mathrm{C}$, and the standard enthalpy of formation of methanol vapor is $-201.2 \mathrm{kJ} / \mathrm{mol} .$ Calculate the vapor pressure of methanol (in $\mathrm{mmHg}$ ) at $25^{\circ} \mathrm{C}$. (Hint: See Appendix 2 for other thermodynamic data of methanol).

David Collins

Numerade Educator

Problem 152

A sample of water shows the following behavior as it is heated at a constant rate:
If twice the mass of water has the same amount of heat transferred to it, which of the following graphs best describes the temperature variation? Note that the scales for all the graphs are the same.

Jake Rempel

Numerade Educator

Problem 153

A closed vessel of volume $9.6 \mathrm{L}$ contains $2.0 \mathrm{g}$ of water. Calculate the temperature (in ^ $\mathrm{C}$ ) at which only half of the water remains in the liquid phase. (See Table 11.5 for vapor pressures of water at different temperatures.)

David Collins

Numerade Educator