Solution: Compare and contrast the structures of the

Consider the following hypothetical data collected in two studies of the reaction 2A(g) 1 2B(g) 88n C(g) 1 2D(g) Time (s) Experiment 1 [A] (mol/L) Experiment 2 [A] (mol/L) 0. 1.0 3 1022 1.0 3 1022 10. 8.4 3 1023 5.0 3 1023 20. 7.1 3 1023 2.5 3 1023 30. ? 1.3 3 1023 40. 5.0 3 1023 6.3 3 1024 In experiment 1, [B] 5 10.0 M. In experiment 2, [B] 5 20.0 M. Rate 5 2d3A4 dt a. Use the concentration versus time data to determine the rate law for the reaction. b. Solve for the rate constant k for the reaction. Include units. c. Calculate the concentration of A in experiment 1 at t 5 30. s. d. The following three mechanisms are proposed for this reaction: i. 2B 34 B2 (Fast equilibrium) B2 1 A 88n E 1 D (Slow) E 1 A 88n C 1 D (Fast) ii. A 1 B 88n D 1 F (Slow) F 1 B 88n C 1 G (Fast) G 1 A 88n D (Fast) iii. A 1 2B 88n E 1 D (Slow) E 1 A 88n C 1 D (Fast) Choose the best mechanism(s). Include an explanation of which mechanism(s) you exclude and why. If you believe two (or even all three) mechanisms are equally good, explain why.

You have learned the difference between intermolecular forces and intramolecular bonds. What if intermolecular forces were stronger than intramolecular bonds? What differences could you observe in the world?

You have seen that the water molecule has a bent shape and therefore is a polar molecule. This accounts for many of waters interesting properties. What if the water molecule was linear? How would this affect the properties of water, such as surface tension, heat of vaporization, and vapor pressure? How would life be different?

Ice is less dense than liquid water, as evidenced by the fact that ice floats in a glass of water. What if ice was more dense than liquid water? How would this affect the phase diagram for water?

It is possible to balance a paper clip on the surface of water in a beaker. If you add a bit of soap to the water, however, the paper clip will sink. Explain how the paper clip can float and why it sinks when soap is added.

Consider a sealed container half-filled with water. Which statement best describes what occurs in the container? a. Water evaporates until the air is saturated with water vapor; at this point, no more water evaporates. b. Water evaporates until the air is overly saturated (supersaturated) with water, and most of this water recondenses; this cycle continues until a certain amount of water vapor is present, and then the cycle ceases. c. The water does not evaporate, because the container is sealed. d. Water evaporates, and then water evaporates and recondenses simultaneously and continuously. e. Water evaporates until it is eventually all in vapor form. Explain each choice, and justify the best choice. For those you did not choose, explain why they are incorrect.

Explain the following: You add 100 mL of water to a 500-mL round-bottom flask and heat the water until it is boiling. You remove the heat, stopper the flask, and the boiling stops. You then run cool water over the neck of the flask, and the boiling begins again. It seems as though you are boiling water by cooling it.

Is it possible for the dispersion forces in a particular substance to be stronger than hydrogen bonding forces in another substance? Explain your answer.

Does the nature of intermolecular forces change when a substance goes from a solid to a liquid or from a liquid to a gas? What causes a substance to undergo a phase change?

Generally, the vapor pressure of a liquid is related to (there may be more than one answer) a. amount of the liquid c. temperature b. atmospheric pressure d. intermolecular forces Explain.

What is meant by the term vapor pressure? Why do liquids have a vapor pressure? Do all liquids have a vapor pressure? What about solids? How does vapor pressure change with changing temperature? Why? What happens, if anything, when the vapor pressure of a liquid is equal to atmospheric pressure?

Consider an open beaker of water. Over time, the water evaporates. As the water is evaporating, is the vapor pressure increasing, decreasing, or staying the same? Why? What is the vapor pressure of water at 1008C? How do you know?

How do the following physical properties depend on the strength of intermolecular forces? Explain. a. surface tension d. boiling point b. viscosity e. vapor pressure c. melting point

Use the kinetic molecular theory to explain why a liquid in an insulated vessel gets cooler as it evaporates.

What are intermolecular forces? How do they differ from intramolecular forces? What are dipoledipole forces? How do typical dipoledipole forces differ from hydrogen-bonding interactions? In what ways are they similar? What are London dispersion forces? How do typical London dispersion forces differ from dipole dipole forces? In what ways are they similar?

List the major types of intermolecular forces in order of increasing strength. Is there some overlap? That is, can the strongest London dispersion forces be greater than some dipoledipole forces? Give examples of such instances.

Why is DHvap for water much greater than DHfus? What does this reveal concerning changes in intermolecular forces in going from solid to liquid to vapor?

Rationalize why chalk (calcium carbonate) has a higher melting point than motor oil (large compounds made from carbon and hydrogen), which has a higher melting point than water, which engages in relatively strong hydrogen-bonding interactions.

Identify the most important types of interparticle forces present in the solids of each of the following substances. a. Ar h. NH4Cl b. HCl i. Teflon, CF3(CF2CF2)nCF3 c. HF j. polyethylene, CH3(CH2CH2)nCH3 d. CaCl2 k. CHCl3 e. CH4 l. NH3 f. CO m. NO g. NaNO3 n. BF3

Predict which substance in each of the following pairs would have the greater intermolecular forces. a. CO2 or OCS b. SeO2 or SO2 c. CH3CH2CH2NH2 or H2NCH2CH2NH2 d. CH3CH3 or H2CO e. CH3OH or H2CO

In each of the following groups of substances, pick the one that has the given property. Justify your answer. a. highest boiling point: HBr, Kr, or Cl2 b. highest freezing point: H2O, NaCl, or HF c. lowest vapor pressure at 258C: Cl2, Br2, or I2 d. lowest freezing point: N2, CO, or CO2 e. lowest boiling point: CH4, CH3CH3, or CH3CH2CH3 f. highest boiling point: HF, HCl, or HBr g. lowest vapor pressure at 258C: CH3CH2CH3, O B CH3CCH3, or CH3CH2CH2OH

In each of the following groups of substances, pick the one that has the given property. Justify each answer. a. highest boiling point: CCl4, CF4, CBr4 b. lowest freezing point: LiF, F2, HCl c. lowest vapor pressure at 258C: CH3OCH3, CH3CH2OH, CH3CH2CH3 d. greatest viscosity: H2S, HF, or H2O2 e. greatest heat of vaporization: H2CO, CH3CH3, CH4 f. smallest enthalpy of fusion: I2, CsBr, or CaO

Rationalize the difference in boiling points for each of the following pairs of substances: a. n-pentane CH3CH2CH2CH2CH3 36.28C neopentane A A O O CH3 CH3 9.5C CH3 3C CH b. HF 208C HCl 2858C c. HCl 2858C LiCl 13608C d. n-pentane CH3CH2CH2CH2CH3 36.28C n-hexane CH3CH2CH2CH2CH2CH3 698C

Rationalize the following differences in physical properties in terms of intermolecular forces. Compare the first three substances with each other, compare the last three with each other, and then compare all six. Can you account for any anomalies? Substance bp (8C) mp (8C) DHvap (kJ/mol) Benzene, C6H6 80 6 33.9 Naphthalene, C10H8 218 80 51.5 Carbon tetrachloride 76 223 31.8 Acetone, CH3COCH3 56 295 31.8 Acetic acid, CH3CO2H 118 17 39.7 Benzoic acid, C6H5CO2H 249 122 68.2

Consider the compounds Cl2, HCl, F2, NaF, and HF. Which compound has a boiling point closest to that of argon? Explain.

Rationalize the following boiling points: CH3C 118C O OH ClCH2C 189C O OH CH3C 57C O OCH3

Consider the following electrostatic potential diagrams: Ethanol Propane Acetone Rank the compounds from

Consider the following electrostatic potential diagrams: Ethanol Propane Acetone Rank the compounds from lowest to highest boiling point, and explain your answer

Consider the following enthalpy changes: F2(g) 1 HF(g) 88n FHF2(g) DH 5 2155 kJ/mol (CH3)2CPO(g) 1 HF(g) 88n (CH3)2CPO,HF(g) DH 5 246 kJ/mol H2O(g) 1 HOH(g) 88n H2O,HOH (in ice) DH 5 221 kJ/mol How do the strengths of hydrogen bonds vary with the electronegativity of the element to which hydrogen is bonded? Where in the preceding series would you expect hydrogen bonds of the following type to fall? O O ,HN OO and G D ,HN OO N G D G D 25. Using the heats of fusion and vaporization for water, calculate the change in enthalpy for the sublimation of water: H2O(s) 88n H2O(g) Using the DH value given in Exercise 24 and the number of hydrogen bonds formed to each water molecule, estimate what portion of the intermolecular forces in ice can be accounted for by hydrogen bonding.

List some physical characteristics that distinguish solids from liquids from gases.

Define the following terms, and describe how each depends on the strength of the intermolecular forces. a. surface tension d. boiling point b. viscosity e. vapor pressure c. melting point

The shape of the meniscus of water in a glass tube is different from that of mercury in a glass tube. Why? H2O in glass Hg in glass

Explain why water forms into beads on a waxed car finish.

Some of the physical properties of H2O and D2O are as follows: Property H2O D2O Density at 208C (g/mL) 0.997 1.108 Boiling point (8C) 100.00 101.41 Melting point (8C) 0.00 3.79 DH8 vap (kJ/mol) 40.7 41.61 DH8fus (kJ/mol) 6.01 6.3 Account for the differences. (Note: D is a symbol often used for 2H, the deuterium isotope of hydrogen.)

Hydrogen peroxide (H2O2) is a syrupy liquid with a relatively low vapor pressure and a normal boiling point of 152.28C. Rationalize the differences between these physical properties and those of water.

Carbon diselenide (CSe2) is a liquid at room temperature. The normal boiling point is 1258C, and the melting point is 245.58C. Carbon disulfide (CS2) is also a liquid at room temperature, with normal boiling and melting points of 46.58C and 2111.68C, respectively. How do the strengths of the intermolecular forces vary from CO2 to CS2 to CSe2? Explain your answer.

Distinguish between the solids in the following pairs. a. crystalline solid and amorphous solid b. ionic solid and molecular solid c. molecular solid and network solid d. metallic solid and network solid

What is closest packing? What is the difference between hexagonal closest packing and cubic closest packing? What is the unit cell for each closest packing arrangement?

Compare and contrast the structures of the following solids. a. diamond and graphite b. silica, silicates, and glass

Compare and contrast the structures of the following solids. a. CO2(s) and H2O(s) b. NaCl(s) and CsCl(s)

Will a crystalline solid or an amorphous solid give a simpler X-ray diffraction pattern? Why?

Boron nitride (BN) exists in two forms. The first is a slippery solid formed from the reaction of BCl3 with NH3, followed by heating in an ammonia atmosphere at 7508C. Subjecting the first form of BN to a pressure of 85,000 atm at 18008C produces a second form that is the second hardest substance known. Both forms of BN remain solids to 30008C. Suggest structures for the two forms of BN.

How could you tell experimentally if TiO2 is an ionic solid or a network solid?

What type of solid will each of the following substances form? a. CO2 e. Ru i. NaOH m. GaAs b. SiO2 f. I2 j. U n. BaO c. Si g. KBr k. CaCO3 o. NO d. CH4 h. H2O l. PH3 p. GeO2

A topaz crystal has an interplanar spacing (d) of 1.36 (1 5 1 3 10210 m). Calculate the wavelength of the X ray that should be used if u 5 15.08 (assume n 5 1)

X rays of wavelength 2.63 were used to analyze a crystal. The angle of first-order diffraction (n 5 1 in the Bragg equation) was 15.558. What is the spacing between crystal planes, and what would be the angle for second-order diffraction (n 5 2)?

X rays from a copper X-ray tube (l 5 1.54 ) were diffracted at an angle of 14.228 by a crystal of silicon. Assuming first-order diffraction (n 5 1 in the Bragg equation), what is the interplanar spacing in silicon?

In what array (simple cubic, body-centered cubic, and face-centered cubic) do atoms pack most efficiently (greatest percent of space occupied by spheres)? Support your answer mathematically.

Calcium has a cubic closest packed structure as a solid. Assuming that calcium has an atomic radius of 197 pm, calculate the density of solid calcium.

A certain form of lead has a cubic closest packed structure with an edge length of 492 pm. Calculate the value of the atomic radius and the density of lead.

Nickel has a face-centered cubic unit cell. The density of nickel is 6.84 g/cm3. Calculate a value for the atomic radius of nickel.

You are given a small bar of an unknown metal X. You find the density of the metal to be 10.5 g/cm3. An X-ray diffraction experiment measures the edge of the facecentered cubic unit cell as 4.09 (1 5 10210 m). Identify X.

Titanium metal has a body-centered cubic unit cell. The density of titanium is 4.50 g/cm3. Calculate the edge length of the unit cell and a value for the atomic radius of titanium. (Hint: In a body-centered arrangement of spheres, the spheres touch along the body diagonal.)

Barium has a body-centered cubic structure. If the atomic radius of barium is 222 pm, calculate the density of solid barium

The radius of gold is 144 pm and the density is 19.32 g/cm3. Does elemental gold have a face-centered cubic structure or a body-centered cubic structure?

The radius of tungsten is 137 pm and the density is 19.3 g/cm3. Does elemental tungsten have a face-centered cubic structure or a body-centered cubic structure?

Use the band model to describe differences among insulators, conductors, and semiconductors. Also use the band model to explain why each of the following increases the conductivity of a semiconductor. a. increasing the temperature b. irradiating with light c. adding an impurity How do conductors and semiconductors differ as to the effect of temperature on electrical conductivity?

How can an n-type semiconductor be produced from pure germanium? How can a p-type semiconductor be produced from pure germanium? Explain how n-type and p-type semiconductors increase electrical conductivity over that of pure germanium.

Explain how a pn junction makes an excellent rectifier

What is an alloy? Explain the differences in structure between substitutional and interstitial alloys. Give an example of each type.

Selenium is a semiconductor used in photocopying machines. What type of semiconductor would be formed if a small amount of indium impurity were added to pure selenium?

The Group 3A/Group 5A semiconductors are composed of equal amounts of atoms from Group 3A and Group 5Afor example, InP and GaAs. These types of semiconductors are used in light-emitting diodes and solidstate lasers. What would you add to make a p-type semiconductor from pure GaAs? How would you dope pure GaAs to make an n-type semiconductor?

The band gap in aluminum phosphide (AlP) is 2.5 electron-volts (1 eV 5 1.6 3 10219 J). What wavelength of light is emitted by an AlP diode?

An aluminum antimonide solid-state laser emits light with a wavelength of 730. nm. Calculate the band gap in joules.

The structures of some common crystalline substances follow. Show that the net composition of each unit cell corresponds to the correct formula of each substance. Cl Na Cl Cs S Zn O Ti

The unit cell for nickel arsenide is shown below. What is the formula of this compound? Ni As

Describe, in general, the structures of ionic solids. Compare and contrast the structures of sodium chloride and zinc sulfide. How many tetrahedral holes and octahedral holes are there per closest packed anion? In zinc sulfide, why are only one-half of the tetrahedral holes filled with cations?

Assume the two-dimensional structure of an ionic compound MxAy is What is the empirical formula of this ionic compound?

Cobalt fluoride crystallizes in a closest packed array of fluoride ions, with the cobalt ions filling one-half of the octahedral holes. What is the formula of this compound?

The compounds Na2O, CdS, and ZrI4 all can be described as cubic closest packed anions with the cations in tetrahedral holes. What fraction of the tetrahedral holes is occupied for each case?

The structure of manganese fluoride can be described as a simple cubic array of manganese ions with fluoride ions at the center of each edge of the cubic unit cell. What is the charge of the manganese ions in this compound?

What is the formula for the compound that crystallizes with a cubic closest packed array of sulfur ions, and that contains zinc ions in 1 8 of the tetrahedral holes and aluminum ions in 1 2 of the octahedral holes?

In solid KCl, the smallest distance between the centers of a potassium ion and a chloride ion is 314 pm. Calculate the length of the edge of the unit cell and the density of KCl, assuming it has the same structure as sodium chloride.

The unit cell of MgO is shown below. Does MgO have a structure like that of NaCl or ZnS? If the density of MgO is 3.58 g/cm3, estimate the radius (in centimeters) of the O22 anions and the Mg21 cations.

The CsCl structure is a simple cubic array of chloride ions with a cesium ion at the center of each cubic array (see Exercise 61). Given that the density of cesium chloride is 3.97 g/cm3, and assuming that the chloride and cesium ions touch along the body diagonal of the cubic unit cell, calculate the distance between the centers of adjacent Cs1 and Cl2 ions in the solid. Compare this value with the expected distance based on the sizes of the ions. The ionic radius of Cs1 is 169 pm, and the ionic radius of Cl2 is 181 pm.

A given sample of wstite has the formula Fe0.950O1.00. Calculate the fraction of iron ions present as Fe31. What fraction of the sites normally occupied by Fe21 must be vacant in this solid?

Use the relative ionic radii in Fig. 13.8 to predict the structures expected for CsBr and KF. Do these predictions agree with observed structures? The ionic radius of Cs1 is 169 pm.

MnO has either the NaCl type structure or the CsCl type structure. The edge length of the MnO unit cell is 4.47 3 1028 cm, and the density of MnO is 5.28 g/cm3. a. Does MnO crystallize in the NaCl type or the CsCl type structure? b. Assuming that the ionic radius of oxygen is 140. pm, estimate the ionic radius of manganese. c. Does the calculated cation-to-anion radius ratio for MnO substantiate your answer in part a? Explain.

Superalloys have been made of nickel and aluminum. The alloy owes its strength to the formation of an ordered phase, called the gamma-prime phase, in which Al atoms are at the corners of a cubic unit cell and Ni atoms are at the face centers. What is the composition (relative numbers of atoms) for this phase of the nickel aluminum superalloy?

The memory metal, nitinol, is an alloy of nickel and titanium. It is called a memory metal because after being deformed, a piece of nitinol wire will return to its original shape. (See Chem. Matters, October 1993, pp. 47.) The structure of nitinol consists of a simple cubic array of Ni atoms and an inner penetrating simple cubic array of Ti atoms. In the extended lattice, a Ti atom is found at the center of a cube of Ni atoms; the reverse is also true. a. Describe the unit cell for nitinol. b. What is the empirical formula of nitinol? c. What are the coordination numbers (number of nearest neighbors) of Ni and Ti in nitinol?

A mineral crystallizes in a cubic closest packed array of oxygen ions with aluminum ions in some of the octahedral holes and magnesium ions in some of the tetrahedral holes. Deduce the formula of this mineral, and predict the fraction of octahedral holes and tetrahedral holes that are filled by the various cations

Perovskite is a mineral containing calcium, titanium, and oxygen. The following diagrams represent the unit cell. Titanium Calcium Oxygen a. What is the formula of perovskite? b. An alternative way of drawing the unit cell of perovskite has calcium at the center of each cubic unit cell. What are the positions of the titanium and oxygen atoms in this representation of the unit cell? Show that the formula for perovskite is the same for both unit cell representations. c. How many oxygen atoms surround a given Ti atom in each representation of the unit cell?

Materials containing the elements Y, Ba, Cu, and O that are superconductors (electrical resistance equals zero) at temperatures above that of liquid nitrogen were recently discovered. The structures of these materials are based on the perovskite structure. Were they to have the ideal perovskite structure, the superconductors would have the structure shown in part (a) of the accompanying figure. Barium Oxygen Copper Yttrium (a) (b) Actual structure of superconductor Ideal perovskite structure a. What is the formula of this ideal perovskite material? b. How is this structure related to the perovskite structure discussed in Exercise 78? These materials, however, do not act as superconductors unless they are deficient in oxygen. The structure of the actual superconducting phase appears to be that shown in part (b) of the figure. c. What is the formula of this material?

Define each of the following. a. evaporation e. melting b. condensation f. enthalpy of vaporization c. sublimation g. enthalpy of fusion d. boiling h. heating curve

What do we mean when we say that a liquid is volatile? Do volatile liquids have large or small vapor pressures at room temperature? What strengths of intermolecular forces occur in highly volatile liquids?

Describe what is meant by dynamic equilibrium in terms of the vapor pressure of a liquid.

How does each of the following affect the rate of evaporation of a liquid in an open dish? a. intermolecular forces b. temperature c. surface area

Consider the following vapor pressure versus temperature plot for three different substances A, B, and C. Pvap (torr) Temperature (C) A B C If the three substances are CH4, SiH4, and NH3, match each curve to the correct substance

A plot of ln (Pvap) versus 1/T (K) is linear with a negative slope. Why is this the case?

In Breckenridge, Colorado, the typical atmospheric pressure is 520. torr. What is the boiling point of water (DHvap 5 40.7 kJ/mol) in Breckenridge? What pressure would have to be applied to steam at 350.8C to condense the steam to liquid water?

Carbon tetrachloride (CCl4) has a vapor pressure of 213 torr at 40.8C and 836 torr at 80.8C. What is the normal boiling point of CCl4?

Diethyl ether (CH3CH2OCH2CH3) was one of the first chemicals used as an anesthetic. At 34.68C, diethyl ether has a vapor pressure of 760. torr, and at 17.98C, it has a vapor pressure of 400. torr. What is the DH of vaporization for diethyl ether?

Plot the following data, and from the graph determine DHvap for magnesium and lithium. In which metal is the bonding stronger? Vapor Pressure (mm Hg) Temperature (8C) Li Mg 1. 750. 620. 10. 890. 740. 100. 1080. 900. 400. 1240. 1040. 760. 1310. 1110.

From the following data for liquid nitric acid, determine its heat of vaporization and normal boiling point. Temperature (8C) Vapor Pressure (mm Hg) 0 14.4 10. 26.6 20. 47.9 30. 81.3 40. 133 50. 208 80. 670.

A substance has the following properties: Specific Heat Capacities DHvap 20 kJ/mol C(s) 3.0 J g21 8C21 DHfus 5.0 kJ/mol C(l) 2.5 J g21 8C21 bp 758C C(g) 1.0 J g21 8C21 mp 2158C Sketch a heating curve for the substance, starting at 2508C.

Use the heatingcooling curve below to answer the following questions. 140 120 100 80 60 40 20 0 Heat added at a constant rate Temperature (C) a. What is the freezing point of the liquid? b. What is the boiling point of the liquid? c. Which is greater, the heat of fusion or the heat of vaporization? Explain each term, and explain how the heatingcooling curve above helps you to answer the question.

How much energy does it take to convert 0.500 kg of ice at 220.8C to steam at 250.8C? Specific heat capacities: ice, 2.1 J g21 8C21; liquid, 4.2 J g21 8C21; steam, 2.0 J g21 8C21; DHvap 5 40.7 kJ/mol; DHfus 5 6.01 kJ/mol.

Consider a 75.0-g sample of H2O(g) at 1258C. What phase or phases are present when 215 kJ of energy is removed from this sample? (See Exercise 93.)

A 0.250-g chunk of sodium metal is cautiously dropped into a mixture of 50.0 g of water and 50.0 g of ice, both at 08C. The reaction is 2Na(s) 1 2H2O(l) 88n 2NaOH(aq) 1 H2(g) DH 5 2368 kJ

A 0.250-g chunk of sodium metal is cautiously dropped into a mixture of 50.0 g of water and 50.0 g of ice, both at 08C. The reaction is 2Na(s) 1 2H2O(l) 88n 2NaOH(aq) 1 H2(g) DH 5 2368 kJ Will the ice melt? Assuming the final mixture has a specific heat capacity of 4.18 J g21 8C21, calculate the final temperature

A 20.0-g sample of ice at 210.08C is mixed with 100.0 g of water at 80.08C. Calculate the final temperature of the mixture assuming no heat loss to the surroundings. The heat capacities of H2O(s) and H2O(l) are 2.08 J g21 8C21 and 4.18 J g21 8C21, respectively, and the enthalpy of fusion for ice is 6.01 kJ/mol.

An ice cube tray contains enough water at 22.08C to make 18 ice cubes, each of which has a mass of 30.0 g. The tray is placed in a freezer that uses CF2Cl2 as a refrigerant. The heat of vaporization of CF2Cl2 is 158 J/g. What mass of CF2Cl2 must be vaporized in the refrigeration cycle to convert all the water at 22.08C to ice at 25.08C? The heat capacities for H2O(s) and H2O(l) are 2.08 J g21 8C21 and 4.18 J g21 8C21, respectively, and the enthalpy of fusion for ice is 6.01 kJ/mol.

In regions with dry climates, evaporative coolers are used to cool air. A typical electric air conditioner is rated at 1.00 3 104 Btu/h (1 Btu, or British thermal unit, equals the amount of energy needed to raise the temperature of 1 lb of water by 18F). How much water must be evaporated each hour to dissipate as much heat as a typical electric air conditioner?

Compare and contrast the phase diagrams of water and carbon dioxide. Why doesnt CO2 have a normal melting point and a normal boiling point, whereas water does? The slopes of the solid/liquid lines in the phase diagrams of H2O and CO2 are different. What do the slopes of the solid/liquid lines indicate in terms of the relative densities of the solid and liquid states for each substance? How do the melting points of H2O and CO2 depend on pressure? How do the boiling points of H2O and CO2 depend on pressure? Rationalize why the critical temperature for H2O is greater than that for CO2.

Define critical temperature and critical pressure. In terms of the kinetic molecular theory, why is it impossible for a substance to exist as a liquid above its critical temperature?

The critical point of NH3 is 1328C and 111 atm, and the critical point of N2 is 21478C and 34 atm. Which of these substances cannot be liquefied at room temperature no matter how much pressure is applied? Explain.

Like most substances, bromine exists in one of the three typical phases. Br2 has a normal melting point of 27.28C and a normal boiling point of 598C. The triple point for Br2 is 27.38C and 40 torr, and the critical point is 3208C and 100 atm. Using this information, sketch a phase diagram for bromine indicating the points described above. Based on your phase diagram, order the three phases from least dense to most dense. What is the stable phase of Br2 at room temperature and 1 atm? Under what temperature conditions can liquid bromine never exist? What phase changes occur as the temperature of a sample of bromine at 0.10 atm is increased from 2508C to 2008C?

Consider the following phase diagram. What phases are present at points A through H? Identify the triple point, normal boiling point, normal freezing point, and critical point. Which phase is denser, solid or liquid? 1.0 atm D E A B F G H C

Use the accompanying phase diagram for sulfur to answer the following questions. (The phase diagram is not to scale.) Temperature Pressure 1 atm 153C, 1420 atm 95.39C, 1 atm 115.21C, 1 atm 444.6C, 1 atm 115.18C, 3.2 105 atm 95.31C, 5.1 106 atm Rhombic Monoclinic Liquid Gas a. How many triple points are in the phase diagram? b. What phases are in equilibrium at each of the triple points? c. What phase is stable at room temperature and 1.0 atm pressure? d. Can monoclinic sulfur exist in equilibrium with sulfur vapor? e. What are the normal melting point and normal boiling point of sulfur? f. Which is the denser solid phase, monoclinic or rhombic sulfur?

Use the accompanying phase diagram for carbon to answer the following questions. a. How many triple points are in the phase diagram? b. What phases can coexist at each triple point? c. What happens if graphite is subjected to very high pressures at room temperature?

Use the accompanying phase diagram for carbon to answer the following questions. a. How many triple points are in the phase diagram? b. What phases can coexist at each triple point? c. What happens if graphite is subjected to very high pressures at room temperature? d. If we assume that the density increases with an increase in pressure, which is more dense, graphite or diamond? 107 109 1011 0 2000 4000 6000 Temperature (K)

Iodine, like most substances, exhibits only three phases: solid, liquid, and vapor. The triple point of iodine is at 90 torr and 1158C. Which of the following statements concerning liquid I2 must be true? Explain your answer. a. I2(l) is more dense than I2(g). b. I2(l) cannot exist above 1158C. c. I2(l) cannot exist at 1 atmosphere pressure. d. I2(l) cannot have a vapor pressure greater than 90 torr. e. I2(l) cannot exist at a pressure of 10 torr.

The melting point of a fictional substance X is 2258C at 10.0 atm. If the density of the solid phase of X is 2.67 g/cm3 and the density of the liquid phase is 2.78 g/cm3 at 10.0 atm, predict whether the normal melting point of X will be less than, equal to, or greater than 2258C. Explain

Consider the following data for xenon: Triple point: 21218C, 280 torr Normal melting point: 21128C Normal boiling point: 21078C Which is more dense, Xe(s) or Xe(l)? How do the melting point and boiling point of xenon depend on pressure?

Some water is placed in a sealed glass container connected to a vacuum pump (a device used to pump gases from a container), and the pump is turned on. The water appears to boil and then freezes. Explain these changes by using the phase diagram for water. What would happen to the ice if the vacuum pump was left on indefinitely?

Oil of wintergreen, or methyl salicylate, has the following structure: O OH mp = 8C C OCH3 Methyl 4-hydroxybenzoate is another molecule with exactly the same molecular formula; it has the following structure: O OH mp = 127C C OCH3 Account for the large difference in the melting points of the two substances.

You have three covalent compounds with three very different boiling points. All of the compounds have similar molar mass and relative shape. Explain how these three compounds could have very different boiling points.

Why is a burn from steam typically much more severe than a burn from boiling water?

When a person has a severe fever, one therapy used to reduce the fever is an alcohol rub. Explain how the evaporation of alcohol from a persons skin removes heat energy from the body

When wet laundry is hung on a clothesline on a cold winter day, it freezes but eventually dries. Explain.

Consider the following data concerning four different substances. Compound Conducts Electricity as a Solid Other Properties B2H6 No Gas at 258C SiO2 No High mp CsI No Aqueous solution Conducts electricity W Yes High mp Label the four substances as either ionic, network, metallic, or molecular solids.

A special vessel (see Fig. 16.52) contains ice and supercooled water (both at 2108C) connected by vapor space. Describe what happens to the amounts of ice and water as time passes

Consider a cation in a trigonal hole. What size ion will just fit in the hole if the packed spheres have radius R?

Use the diagram of the unit cell for the hexagonal closest packed structure in Fig. 16.14 to determine the net number of atoms in the hcp unit cell.

Argon has a cubic closest packed structure as a solid. Assuming that argon has a radius of 190. pm, calculate the density of solid argon.

Rubidium chloride has the sodium chloride structure at normal pressures but assumes the cesium chloride structure at high pressures. What ratio of densities is expected for these two forms? Does this change in structure make sense on the basis of simple models?

A certain oxide of titanium is 28.31% oxygen by mass and contains a mixture of Ti21 and Ti31 ions. Determine the formula of the compound and the relative numbers of Ti21 and Ti31 ions.

Spinel is a mineral that contains 37.9% aluminum, 17.1% magnesium, and 45.0% oxygen, by mass, and has a density of 3.57 g/cm3. The edge of the cubic unit cell measures 809 pm. How many of each type of atom are present in the unit cell?

A metallic solid with atoms in a face-centered cubic unit cell with an edge length of 392 pm has a density of 21.45 g/cm3. Calculate the atomic mass and the atomic radius of the metal. Identify the metal.

The unit cell for a pure xenon fluoride compound is shown below. What is the formula of the compound? Xenon Fluorine

A 0.132-mole sample of an unknown semiconducting material with the formula XY has a mass of 19.0 g. The element X has an electron configuration of [Kr]5s24d10. What is this semiconducting material? A small amount of the Y atoms in the semiconductor is replaced with an equivalent amount of atoms with an electron configuration of [Ar]4s23d104p5. Does this correspond to n-type or p-type doping?

Consider the following melting point data: Compound mp (8C) NaCl 801 MgCl2 708 AlCl3 190 SiCl4 270 PCl3 291 SCl2 278 Cl2 2101 Compound mp (8C) NaF 997 MgF2 1396 AlF3 1040 SiF4 290 PF5 294 SF6 256 F2 2220 Account for the trends in melting points in terms of interparticle forces.

When 1 mole of benzene is vaporized at a constant pressure of 1.00 atm and at its boiling point of 353.0 K, 30.79 kJ of energy (heat) is absorbed and the volume change is 128.90 L. What are DE and DH for this process?

The temperature inside a pressure cooker is 1158C. Calculate the vapor pressure of water inside the pressure cooker. What would be the temperature inside the pressure cooker if the vapor pressure of water was 3.50 atm?

Dry nitrogen gas is bubbled through liquid benzene (C6H6) at 20.08C. From 100.0 L of the gaseous mixture of nitrogen and benzene, 24.7 g of benzene is condensed by passing the mixture through a trap at a temperature where nitrogen is gaseous and the vapor pressure of benzene is negligible. What is the vapor pressure of benzene at 20.08C?

A sample of dry nitrogen gas weighing 100.0 g is bubbled through liquid water at 25.08C. The gaseous mixture of nitrogen and water vapor escapes at a total pressure of 700. torr. What mass of water has vaporized? (The vapor pressure of water at 258C is 23.8 torr.)

The molar enthalpy of vaporization of water at 373 K is 41.16 kJ/mol. What fraction of this energy is used to change the internal energy of the water, and what fraction is used to do work against the atmosphere? (Assume that water vapor is an ideal gas.)

You are asked to help set up a historical display in the park by stacking some cannonballs next to a Revolutionary War cannon. You are told to stack them by starting with a triangle in which each side is composed of four touching cannonballs. You are to continue stacking them until you have a single ball on the top centered over the middle of the triangular base. a. How many cannonballs do you need? b. What type of closest packing arrangement is displayed by the cannonballs? c. The four corners of the pyramid of cannonballs form the corners of what type of regular geometric solid?

Consider the ionic solid AxBy, which has the unit cell below. The B ions are packed in a cubic arrangement, where each face has this structure: There is one B in the center of the cube. The structure can also be described in terms of three parallel planes of Bs of the type shown above. The resulting structure thus contains eight intersecting cubes of Bs. The A ions are found in the centers of alternate intersecting cubes (that is, four of every eight cubes have As in the center). What is the formula of AxBy? In the extended structure, how many Bs surround each A? What structure do the Bs form?

Mn crystallizes in the same type of cubic unit cell as Cu. Assuming that the radius of Mn is 5.6% larger than the radius of Cu and the density of Cu is 8.96 g/cm3, calculate the density of Mn.

Which of the following compound(s) exhibit only London dispersion intermolecular forces? Which compound(s) exhibit hydrogen-bonding forces? Considering only the compounds without hydrogen-bonding interactions, which compounds have dipoledipole intermolecular forces? a. SF4 d. HF b. CO2 e. ICl5 c. CH3CH2OH f. XeF4

Which of the following statements about intermolecular forces is(are) true? a. London dispersion forces are the only type of intermolecular force that nonpolar molecules exhibit. b. Molecules that have only London dispersion forces will always be gases at room temperature (258C). c. The hydrogen-bonding forces in NH3 are stronger than those in H2O. d. The molecules in SO2(g) exhibit dipoledipole intermolecular interactions. e. CH3CH2CH3 has stronger London dispersion forces than does CH4.

Which of the following statements is(are) true? a. LiF will have a higher vapor pressure at 258C than H2S. b. HF will have a lower vapor pressure at 2508C than HBr. c. Cl2 will have a higher boiling point than Ar. d. HCl is more soluble in water than in CCl4. e. MgO will have a higher vapor pressure at 258C than CH3CH2OH

Aluminum has an atomic radius of 143 pm and forms a solid with a cubic closest packed structure. Calculate the density of solid aluminum in g/cm3.

Pyrolusite is a mineral containing manganese ions and oxide ions. Its structure can best be described as a bodycentered cubic array of manganese ions with two oxide ions inside the unit cell and two oxide ions each on two faces of the cubic unit cell. What is the charge on the manganese ions in pyrolusite?

The structure of the compound K2O is best described as a cubic closest packed array of oxide ions with the potassium ions in tetrahedral holes. What percent of the tetrahedral holes are occupied in this solid?

What type of solid (network, metallic, Group 8A, ionic, or molecular) will each of the following substances form? a. Kr d. SiO2 b. SO2 e. NH3 c. Ni f. Pt

Some ice cubes at 08C with a total mass of 403 g are placed in a microwave oven and subjected to 750. W (750. J/s) of energy for 5.00 minutes. What is the final temperature of the water? Assume all the energy of the microwave is absorbed by the water, and assume no heat loss by the water.

The enthalpy of vaporization for acetone is 32.0 kJ/mol. The normal boiling point for acetone is 56.58C. What is the vapor pressure of acetone at 23.58C?

Choose the statements that correctly describe the following phase diagram. 1.0 100 200 300 T (K) P (atm) 400 2.0 a. If the temperature is raised from 50 K to 400 K at a pressure of 1 atm, the substance boils at approximately 185 K. b. The liquid phase of this substance cannot exist under conditions of 2 atm at any temperature. c. The triple point occurs at approximately 165 K. d. At a pressure of 1.5 atm, the melting point of the substance is approximately 370 K. e. The critical point occurs at approximately 1.7 atm and 410 K.

An electron is trapped in an octahedral hole in a closest packed array of aluminum atoms (assume they behave as uniform hard spheres). In this situation, the energy of the electron is quantized and the lowest-energy transition corresponds to a wavelength of 9.50 nm. Assuming that the hole can be approximated as a cube, what is the radius of a sphere that will just fit in the octahedral hole? Reference Exercise 164 in Chapter 12 for the energy equation for a particle in a cube

You and a friend each synthesize a compound with the formula XeCl2F2. Your compound is a liquid, and your friends compound is a gas (at the same conditions of temperature and pressure). Explain how the two compounds with the same formulas can exist in different phases at the same conditions of pressure and temperature.

A metal burns in air at 6008C under high pressure to form an oxide with formula MO2. This compound is 23.72% oxygen by mass. The distance between the centers of touching atoms in a cubic closest packed crystal of this metal is 269.0 pm. What is this metal? What is its density?

Consider a perfectly insulated and sealed container. Determine the minimum volume of a container such that a gallon of water at 258C will evaporate completely. If the container is a cube, determine the dimensions in feet. Assume the density of water is 0.998 g/cm3.

The vapor pressure of water at 30.08C is 31.824 torr; at this temperature the density of liquid water is 0.99567 g/cm3. What is the ratio of the average distance between water molecules in the liquid and in the saturated vapor at this temperature?

For a simple cubic array, solve for the volume of an interior sphere (cubic hole) in terms of the radius of a sphere in the array

The structures of another class of high-temperature ceramic superconductors are shown below. (a) Ca (b) (c) (d) Ba Cu Tl O a. Determine the formula of each of these four superconductors. b. One of the structural features that appears to be essential for high-temperature superconductivity is the presence of planar sheets of copper and oxygen atoms. As the number of sheets in each unit cell increases, the temperature for the onset of superconductivity increases. Order the four structures from the lowest to highest superconducting temperature. c. Assign oxidation states to Cu in each structure assuming that Tl exists as Tl31. The oxidation states of Ca, Ba, and O are assumed to be 12, 12, and 22, respectively. d. It also appears that copper must display a mixture of oxidation states for a material to exhibit superconductivity. Explain how this occurs in these materials as well as in the superconductor in Exercise 79.

Consider two different compounds, each with the formula C2H6O. One of these compounds is a liquid at room conditions and the other is a gas. Write Lewis structures consistent with this observation, and explain your answer.

The edge of the LiCl unit cell is 514 pm in length. Assuming that the Li1 ions just fit in the octahedral holes of the closest packed Cl2 ions, calculate the ionic radii for the Li1 and Cl2 ions. Compare them with the radii given in Fig. 13.8, and discuss the significance of any discrepancies.

The table below lists the ionic radii for the cations and anions in three different ionic compounds. Formula rcation ranion SnO2 71 pm 140. pm AlP 50. pm 212. pm BaO 135 pm 140. pm Each compound has either the NaCl, CsCl, or ZnS type cubic structure. Predict the type of structure formed (NaCl, CsCl, or ZnS) and the type and fraction of holes filled by the cations, and estimate the density of each compound.