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Chapter 11

Liquids, Solids, and Intermolecular Forces

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Problem 1

Why do ethanol and dimethyl ether have such different properties even though they have the same chemical formula?

Lizabeth T.
Numerade Educator

Problem 2

Why are intermolecular forces important?

Nicholas W.
Numerade Educator

Problem 3

What are the key properties of liquids (in contrast to gases and solids)?

Lizabeth T.
Numerade Educator

Problem 4

What are the key properties of solids (in contrast to liquids and gases)?

Nicholas W.
Numerade Educator

Problem 5

What is the fundamental difference between an amorphous solid and a crystalline solid?

Lizabeth T.
Numerade Educator

Problem 6

Which factors cause transitions between the solid and liquid state? The liquid and gas state?

Nicholas W.
Numerade Educator

Problem 7

Describe the relationship between the state of a substance, its temperature, and the strength of its intermolecular forces.

Lizabeth T.
Numerade Educator

Problem 8

From which kinds of interactions do intermolecular forces originate?

Nicholas W.
Numerade Educator

Problem 9

Why are intermolecular forces generally much weaker than bonding forces?

Lizabeth T.
Numerade Educator

Problem 10

What is the dispersion force? What does the magnitude of the dispersion force depend on? How can we predict the magnitude of the dispersion force for closely related elements or compounds?

Nicholas W.
Numerade Educator

Problem 11

What is the dipole-dipole force? How can we predict the presence of dipole-dipole forces in a compound?

Lizabeth T.
Numerade Educator

Problem 12

How is the miscibility of two liquids related to their polarity?

Nicholas W.
Numerade Educator

Problem 13

What is hydrogen bonding? How can we predict the presence of hydrogen bonding in a compound?

Lizabeth T.
Numerade Educator

Problem 14

What is the ion-dipole force? Why is it important?

Nicholas W.
Numerade Educator

Problem 15

What is surface tension? How does surface tension result from intermolecular forces? How is it related to the strength of intermolecular forces?

Lizabeth T.
Numerade Educator

Problem 16

What is viscosity? How does viscosity depend on intermolecular forces? What other factors affect viscosity?

Nicholas W.
Numerade Educator

Problem 17

What is capillary action? How does it depend on the relative strengths of adhesive and cohesive forces?

Lizabeth T.
Numerade Educator

Problem 18

Explain what happens during the processes of vaporization and condensation. Why does the rate of vaporization increase with increasing temperature and surface area?

Nicholas W.
Numerade Educator

Problem 19

Why is vaporization endothermic? Why is condensation exothermic?

Lizabeth T.
Numerade Educator

Problem 20

How is the volatility of a substance related to the intermolecular forces present within the substance?

Nicholas W.
Numerade Educator

Problem 21

What is the heat of vaporization for a liquid, and why is it useful?

Lizabeth T.
Numerade Educator

Problem 22

Explain the process of dynamic equilibrium. How is dynamic equilibrium related to vapor pressure?

Nicholas W.
Numerade Educator

Problem 23

What happens to a system in dynamic equilibrium when it is disturbed in some way?

Lizabeth T.
Numerade Educator

Problem 24

How is vapor pressure related to temperature? What happens to the vapor pressure of a substance when the temperature is increased? Decreased?

Nicholas W.
Numerade Educator

Problem 25

Define the terms boiling point and normal boiling point.

Lizabeth T.
Numerade Educator

Problem 26

What is the Clausius-Clapeyron equation, and why is it important?

Nicholas W.
Numerade Educator

Problem 27

Explain what happens to a substance when it is heated in a closed container to its critical temperature.

Lizabeth T.
Numerade Educator

Problem 28

What is sublimation? Cite a common example of sublimation.

Nicholas W.
Numerade Educator

Problem 29

What is fusion? Is fusion exothermic or endothermic? Why?

Lizabeth T.
Numerade Educator

Problem 30

What is the heat of fusion, and why is it important?

Nicholas W.
Numerade Educator

Problem 31

Examine the heating curve for water in Section 11.7 (Figure 11.33). Explain why the curve has two segments in which heat is added to the water but the temperature does not rise.

Lizabeth T.
Numerade Educator

Problem 32

Examine the heating curve for water in Section 11.7 (Figure 11.33). Explain the significance of the slopes of each of the three rising segments. Why are the slopes different?

Nicholas W.
Numerade Educator

Problem 33

What is a phase diagram? What is the significance of crossing a line in a phase diagram?

Lizabeth T.
Numerade Educator

Problem 34

Draw a generic phase diagram and label its important features.

Nicholas W.
Numerade Educator

Problem 35

Determine the kinds of intermolecular forces that are present in each element or compound.
a. N2
b. NH3
c. CO
d. CCl4

Lizabeth T.
Numerade Educator

Problem 36

Determine the kinds of intermolecular forces that are present in each element or compound.
a. Kr
b. NCl3
c. SiH4
d. HF

Antwan D.
Numerade Educator

Problem 37

Determine the kinds of intermolecular forces that are present in each element or compound.
a. HCl
b. H2O
c. Br2
d. He

Lizabeth T.
Numerade Educator

Problem 38

Determine the kinds of intermolecular forces that are present in each element or compound.
a. PH3
b. HBr
c. CH3OH
d. I2

Charotte M.
Numerade Educator

Problem 39

Arrange these compounds in order of increasing boiling point.
Explain your reasoning.
a. CH
b. CH3CH3
c. CH3CH2Cl
d. CH3CH2OH

Lizabeth T.
Numerade Educator

Problem 40

Arrange these compounds in order of increasing boiling point.
Explain your reasoning.
a. H2S
b. H2Se
c. H2O

Nicholas W.
Numerade Educator

Problem 41

Pick the compound with the highest boiling point in each pair.
Explain your reasoning.
a. CH3OH or CH3SH
b. CH3OCH3 or CH3CH2OH
c. CH4 or CH3CH3

Charotte M.
Numerade Educator

Problem 42

Pick the compound with the highest boiling point in each pair.
Explain your reasoning.
a. NH3 or CH4
b. CS2 or CO2
c. CO2 or NO2

NB
Nothando B.
Numerade Educator

Problem 43

In each pair of compounds, pick the one with the higher vapor pressure at a given temperature. Explain your reasoning.
a. Br2 or I2
b. H2S or H2O
c. NH3 or PH3

Lizabeth T.
Numerade Educator

Problem 44

In each pair of compounds, pick the one with the higher vapor pressure at a given temperature. Explain your reasoning.
a. CH4 or CH3Cl
b. CH3CH2CH2OH or CH3OH
c. CH3OH or H2CO

Charotte M.
Numerade Educator

Problem 45

Determine if each pair of compounds forms a homogeneous solution when combined. For those that form homogeneous solutions, indicate the type of forces that are involved.
a. CCl4 and H2O
b. KCl and H2O
c. Br2 and CCl4
d. CH3CH2OH and H2O

Lizabeth T.
Numerade Educator

Problem 46

Determine if each pair of compounds forms a homogeneous solution when combined. For those that form homogeneous solutions, indicate the type of forces that are involved.
a. CH3CH2CH2CH2CH3 and CH3CH2CH2CH2CH2CH3
b. CBr4 and H2O
c. LiNO3 and H2O
d. CH3OH and CH3CH2CH2CH2CH3

David C.
Numerade Educator

Problem 47

Which compound would you expect to have greater surface tension: acetone [(CH3)2CO] or water (H2O)? Explain.

Lizabeth T.
Numerade Educator

Problem 48

Water (a) "wets" some surfaces and beads up on others. Mercury (b), in contrast, beads up on almost all surfaces. Explain this difference

Nicholas W.
Numerade Educator

Problem 49

The structures of two isomers of heptane are shown here. Which of these two compounds would you expect to have the greater viscosity?

Lizabeth T.
Numerade Educator

Problem 50

The viscosity of a multigrade motor oil (such as one rated 10W-40) is less temperature dependent than the viscosities of most substances. These oils contain polymers (long molecules composed of repeating units) that coil up at low temperatures but unwind at higher temperatures. Explain how the addition of
these polymers to the motor oil might make the viscosity less temperature dependent than a normal liquid.

Nicholas W.
Numerade Educator

Problem 51

Water in a glass tube that contains grease or oil residue displays a flat meniscus (the tube on the left in the accompanying photo), whereas water in a clean glass tube displays a concave meniscus (the tube on the right). Explain this observation.

Lizabeth T.
Numerade Educator

Problem 52

When a thin glass tube is put into water, the water rises 1.4 cm. When the same tube is put into hexane, the hexane rises only 0.4cm. Explain.

Nicholas W.
Numerade Educator

Problem 53

Which evaporates more quickly: 55 mL of water in a beaker with a diameter of 4.5 cm or 55 mL of water in a dish with a diameter of 12 cm? Is the vapor pressure of the water different in the two containers? Explain.

Lizabeth T.
Numerade Educator

Problem 54

Which evaporates more quickly: 55 mL of water (H2O) in a beaker or 55 mL of acetone [(CH3)2CO] in an identical beaker under identical conditions? Is the vapor pressure of the two substances different? Explain.

Nicholas W.
Numerade Educator

Problem 55

Spilling room-temperature water over your skin on a hot day cools you down. Spilling room-temperature vegetable oil over your skin on a hot day does not. Explain the difference.

Lizabeth T.
Numerade Educator

Problem 56

Why is the heat of vaporization of water greater at room temperature than it is at its boiling point?

Nicholas W.
Numerade Educator

Problem 57

The human body obtains 915 kJ of energy from a candy bar. If this energy were used to vaporize water at 100 C, how much water (in liters) could be vaporized? (Assume the density of water is 1.00 g>mL.)

Lizabeth T.
Numerade Educator

Problem 58

A 100.0 mL sample of water is heated to its boiling point. How much heat (in kJ) is required to vaporize it? (Assume a density of 1.00 g>mL.)

Nicholas W.
Numerade Educator

Problem 59

Suppose that 0.95 g of water condenses on a 75.0 g block of iron that is initially at 22 C. If the heat released during condensation is used only to warm the iron block, what is the final temperature (in C) of the iron block? (Assume a constant enthalpy of vaporization for water of 44.0 kJ/mol.)

Lizabeth T.
Numerade Educator

Problem 60

Suppose that 1.15 g of rubbing alcohol (C3H8O) evaporates from a 65.0 g aluminum block. If the aluminum block is initially at 25 C, what is the final temperature of the block after the evaporation of the alcohol? Assume that the heat required for the vaporization of the alcohol comes only from the aluminum block and that the alcohol vaporizes at 25 C.

Nicholas W.
Numerade Educator

Problem 61

This table displays the vapor pressure of ammonia at several different temperatures. Use the data to determine the heat of vaporization and normal boiling point of ammonia.

Lizabeth T.
Numerade Educator

Problem 62

This table displays the vapor pressure of nitrogen at several different temperatures. Use the data to determine the heat of vaporization and normal boiling point of nitrogen.

Nicholas W.
Numerade Educator

Problem 63

Ethanol has a heat of vaporization of 38.56 kJ>mol and a normal boiling point of 78.4 C. What is the vapor pressure of ethanol at15 C?

Lizabeth T.
Numerade Educator

Problem 64

Benzene has a heat of vaporization of 30.72 kJ>mol and a normal boiling point of 80.1 C. At what temperature does benzene boil when the external pressure is 445 torr?

Nicholas W.
Numerade Educator

Problem 65

How much energy is released when 65.8 g of water freezes?

Lizabeth T.
Numerade Educator

Problem 66

Calculate the amount of heat required to completely sublime
50.0g of solid dry ice (CO2) at its sublimation temperature. The
heat of sublimation for carbon dioxide is 32.3 kJ/mol.

Nicholas W.
Numerade Educator

Problem 67

An 8.5 g ice cube is placed into 255 g of water. Calculate the temperature change in the water upon the complete melting of the ice. Assume that all of the energy required to melt the ice comes from the water.

Lizabeth T.
Numerade Educator

Problem 68

How much ice (in grams) would have to melt to lower the temperature of 352 mL of water from 25 C to 5 C? (Assume the density of water is 1.0 g>mL.)

Nicholas W.
Numerade Educator

Problem 69

How much heat (in kJ) is required to warm 10.0 g of ice, initially at -10.0 C, to steam at 110.0 C? The heat capacity of ice is 2.09 J>g # C, and that of steam is 2.01 J>g # C.

Lizabeth T.
Numerade Educator

Problem 70

How much heat (in kJ) is evolved in converting 1.00 mol of steam at 145 C to ice at -50 C? The heat capacity of steam is 2.01 J/g # C, and that of ice is 2.09 J/g # C.

Nicholas W.
Numerade Educator

Problem 71

Identify the states present at points a through g in the phase diagram shown here.

Lizabeth T.
Numerade Educator

Problem 72

Consider the phase diagram for iodine shown at the top of the next page.
a. What is the normal boiling point for iodine?
b. What is the melting point for iodine at 1 atm?
c. Which state is present at room temperature and normal atmospheric pressure?
d. Which state is present at 186 C and 1.0 atm?

Nicholas W.
Numerade Educator

Problem 73

Nitrogen has a normal boiling point of 77.3 K and a melting point (at 1 atm) of 63.1 K. Its critical temperature is 126.2 K, and its critical pressure is 2.55 * 104 torr. It has a triple point at 63.1 K and 94.0 torr. Sketch the phase diagram for nitrogen. Does nitrogen have a stable liquid state at 1 atm?

Lizabeth T.
Numerade Educator

Problem 74

Argon has a normal boiling point of 87.2 K and a melting point (at 1 atm) of 84.1 K. Its critical temperature is 150.8 K, and its critical pressure is 48.3 atm. It has a triple point at 83.7 K and 0.68 atm. Sketch the phase diagram for argon. Which has the greater density, solid argon or liquid argon?

Nicholas W.
Numerade Educator

Problem 75

Consider the phase diagram for sulfur shown here. The rhombic and monoclinic states are two solid states with different structures.
a. Below what pressure does solid sulfur sublime?
b. Which of the two solid states of sulfur is most dense?

Lizabeth T.
Numerade Educator

Problem 76

The high-pressure phase diagram of ice is shown here. Notice that, under high pressure, ice can exist in several different solid forms. Which three forms of ice are present at the triple point marked O? What is the density of ice II compared to ice I (the familiar form of ice)? Would ice III sink or float in liquid water?

Nicholas W.
Numerade Educator

Problem 77

Water has a high boiling point given its relatively low molar mass. Explain.

Lizabeth T.
Numerade Educator

Problem 78

Water is a good solvent for many substances. What is the molecular basis for this property, and why is it significant?

Nicholas W.
Numerade Educator

Problem 79

Explain the role water plays in moderating Earth's climate.

Lizabeth T.
Numerade Educator

Problem 80

How is the density of solid water compared to that of liquid water atypical among substances? Why is this significant?

Nicholas W.
Numerade Educator

Problem 81

Explain the observed trend in the melting points of the hydrogen halides.
HI -50.8 C
HBr -88.5 C
HCl -114.8 C
HF -83.1 C

Lizabeth T.
Numerade Educator

Problem 82

Explain the observed trend in the boiling points of these compounds.
H2Te -2 C
H2Se -41.5 C
H2S -60.7 C
H2O 100 C

Nicholas W.
Numerade Educator

Problem 83

The vapor pressure of water at 25 C is 23.76 torr. If 1.25 g of water is enclosed in a 1.5 L container, is any liquid present? If so, what is the mass of the liquid?

Lizabeth T.
Numerade Educator

Problem 84

The vapor pressure of CCl3F at 300 K is 856 torr. If 11.5 g of CCl3F is enclosed in a 1.0 L container, is any liquid present? If so, what is the mass of the liquid?

Nicholas W.
Numerade Educator

Problem 85

Four ice cubes at exactly 0 C with a total mass of 53.5 g are combined with 115 g of water at 75 C in an insulated container. If no heat is lost to the surroundings, what is the final temperature of the mixture?

Lizabeth T.
Numerade Educator

Problem 86

A sample of steam with a mass of 0.552 g at a temperature of 100 C condenses into an insulated container holding 4.25 g of water at 5.0 C. Assuming that no heat is lost to the surroundings, what is the final temperature of the mixture?

Nicholas W.
Numerade Educator

Problem 87

Draw a heating curve (such as the one in Figure 11.33) for 1 mole of methanol beginning at 170 K and ending at 350 K. Assume that the values given here are constant over the relevant temperature ranges.

Lizabeth T.
Numerade Educator

Problem 88

Draw a heating curve (such as the one in Figure 11.33) for 1 mol of benzene beginning at 0 C and ending at 100 C. Assume that the values given here are constant over the relevant temperature ranges.

Nicholas W.
Numerade Educator

Problem 89

Air conditioners not only cool air but dry it as well. A room in a home measures 6.0 m * 10.0 m * 2.2 m. If the outdoor temperature is 30 C and the vapor pressure of water in the air is 85% of the vapor pressure of water at this temperature, what mass of water must be removed from the air each time the volume of air in the room cycles through the air conditioner? The vapor pressure for water at 30 C is 31.8 torr.

Aadit S.
Numerade Educator

Problem 90

A sealed flask contains 0.55 g of water at 28 C. The vapor pressure of water at this temperature is 28.36 mmHg. What is the minimum volume of the flask in order that there is no liquid water present in the flask?

Nicholas W.
Numerade Educator

Problem 91

Two liquids, A and B, have vapor pressures at a given temperature of 24 mmHg and 36 mmHg, respectively. We prepare solutions of A and B at a given temperature and measure the total pressures above the solutions. We obtain these data:

Predict the total pressure above a solution of 5 mol A and 1 mol B.

Lizabeth T.
Numerade Educator

Problem 92

Butane (C4H10) has a heat of vaporization of 22.44 kJ>mol and a normal boiling point of -0.4 C. A 250.0 mL sealed flask contains 0.55 g of butane at -22 C. How much liquid butane is present? If the butane is warmed to 25 C, how much liquid butane is present?

Nicholas W.
Numerade Educator

Problem 93

Liquid nitrogen can be used as a cryogenic substance to obtain low temperatures. Under atmospheric pressure, liquid nitrogen boils at 77 K, allowing low temperatures to be reached. However, if the nitrogen is placed in a sealed, insulated container connected to a vacuum pump, even lower temperatures can be reached. Why? If the vacuum pump has sufficient capacity and is left on for an extended period of time, the liquid nitrogen starts to freeze. Explain.

Lizabeth T.
Numerade Educator

Problem 94

Given that the heat of fusion of water is -6.02 kJ>mol, the heat capacity of H2O(l) is 75.2 J>mol # K, and the heat capacity of H2O(s) is 37.7 J>mol # K, calculate the heat of fusion of water at -10 C.

Nicholas W.
Numerade Educator

Problem 95

The heat of combustion of CH4 is 890.4 kJ>mol, and the heat capacity of H2O is 75.2 J>mol # K. Find the volume of methane measured at 298 K and 1.00 atm required to convert 1.00 L of water at 298 K to water vapor at 373 K.

Stephen H.
Numerade Educator

Problem 96

Three 1.0-L flasks, maintained at 308 K, are connected to each other with stopcocks. Initially, the stopcocks are closed. One of the flasks contains 1.0 atm of N2; the second, 2.0 g of H2O; and the third, 0.50 g of ethanol, C2H6O. The vapor pressure of H2O at 308 K is 42 mmHg, and that of ethanol is 102 mmHg. When the stopcocks are opened and the contents mix freely, what is the pressure?

Nicholas W.
Numerade Educator

Problem 97

One prediction of global warming is the melting of global ice, which may result in coastal flooding. A criticism of this prediction is that the melting of icebergs does not increase ocean levels any more than the melting of ice in a glass of water increases the level of liquid in the glass. Is this a valid criticism? Does the melting of an ice cube in a cup of water raise the level of the liquid in the cup? Why or why not? In response to this criticism, scientists have asserted that they are not worried about melting icebergs, but rather the melting of ice sheets that sit on the continent of Antarctica. Would the melting of this ice increase ocean levels? Why or why not?

Lizabeth T.
Numerade Educator

Problem 98

The rate of vaporization depends on the surface area of the liquid. However, the vapor pressure of a liquid does not depend on the surface area. Explain.

Nicholas W.
Numerade Educator

Problem 99

Substance A has a smaller heat of vaporization than substance B. Which of the two substances undergoes a larger change in vapor pressure for a given change in temperature?

Lizabeth T.
Numerade Educator

Problem 100

A substance has a heat of vaporization of Hvap and heat of fusion of Hfus. Express the heat of sublimation in terms of Hvap and Hfus.

Nicholas W.
Numerade Educator

Problem 101

Examine the heating curve for water in Section 11.7 (Figure11.33). If heat is added to the water at a constant rate, which of the three segments in which temperature is rising will have the least steep slope? Why?

Lizabeth T.
Numerade Educator

Problem 102

A root cellar is an underground chamber used to store fruits, vegetables, and sometimes meats. In extreme cold, farmers put large vats of water into the root cellar to prevent fruits and vegetables from freezing. Explain why this works.

Nicholas W.
Numerade Educator

Problem 103

Suggest an explanation for the observation that the heat of fusion of a substance is always smaller than its heat of vaporization.

Lizabeth T.
Numerade Educator

Problem 104

Refer to Figure 11.33 to answer each question.
a. A sample of steam begins on the line segment labeled 5 on the graph. Is heat absorbed or released in moving from the line segment labeled 5 to the line segment labeled 3? What is the sign of q for this change?
b. In moving from left to right along the line segment labeled 2 on the graph, heat is absorbed, but the temperature remains constant. Where does the heat go?
c. How would the graph change if it were for another substance (other than water)?

Nicholas W.
Numerade Educator

Problem 105

The following image is an electrostatic potential map for ethylene oxide, (CH2)2O, a polar molecule. Use the electrostatic potential map to predict the geometry for how one ethylene oxide molecule interacts with another. Draw structural formulas, using the three-dimensional bond notation introduced in Section 5.9, to show the geometry of the interaction.

Snow P.
Numerade Educator

Problem 106

A substance has a triple point at a temperature of 17 C and a pressure of 3.2 atmospheres. In which states can the substance exist on the surface of Earth at sea level (open to the atmosphere)?

Nicholas W.
Numerade Educator

Problem 107

The boiling points of three compounds are tabulated here.

Answer the following questions without looking up the structures for these molecules: Which compound experiences hydrogen bonding? Which compound is polar but does not experience hydrogen bonding? Which is neither polar nor capable of hydrogen bonding? Explain your answers.

Lizabeth T.
Numerade Educator

Problem 108

The vapor pressure for pure water and pure acetone is measured as a function of temperature. In each case, a graph of the log of the vapor pressure versus 1>T is found to be a straight line. The slope of the line for water is -4895 K, and the slope of the line for acetone is -6748 K. Determine H vap for each substance. Account for the difference by discussing the molecular structure of the two molecules.

Nicholas W.
Numerade Educator

Problem 109

Based on the heating curve for water, does it take more energy to melt a mole of water or to boil a mole of water? Does it take more energy to warm the solid, the liquid, or the gas by 10 C? Explain your answers clearly.

Lizabeth T.
Numerade Educator

Problem 110

Sketch the phase diagram for carbon dioxide. If you have carbon dioxide at 1.0 atm and 25 C, could you turn it into a liquid by cooling it down? How could you make it a liquid at 25 C? If you increase the pressure of carbon dioxide that is at body temperature (37 C), will it ever liquefy?

Nicholas W.
Numerade Educator

Problem 111

We have seen that molar mass and molecular structure influence the boiling point. We can see these two factors at work in the boiling points of the Group 6A hydrides shown in the graph.

In order to disentangle the effects of molar mass and molecular structure on boiling point, consider the data in the table.

Use the information in the graph and the table to answer the questions.
a. Does molar mass alone correlate with the trend in the boiling points for the Group 6A hydrides?
b. Which boiling points in the graph correlate with polarizability? Which type of intermolecular force correlates with polarizability?
c. Use the data in the table to explain the anomalously high boiling point of water.

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