Which has the greater polarizability? Explain. (a) Br2 or I2 (b) CH2CH2 or CH3CH3 (c)

How does the energy of attraction between particles compare with their energy of motion in a gas and in a solid? As part of your answer, identify two macroscopic properties that differ between a gas and a solid.

(a) Why are gases more easily compressed than liquids? (b) Why do liquids have a greater ability to flow than solids?

What type of forces, intramolecular or intermolecular: (a) Prevent ice cubes from adopting the shape of their container? (b) Are overcome when ice melts? (c) Are overcome when liquid water is vaporized? (d) Are overcome when gaseous water is converted to hydrogen gas and oxygen gas?

(a) Why is the heat of fusion (DHfus) of a substance smaller than its heat of vaporization (DHvap)? (b) Why is the heat of sublimation (DHsubl) of a substance greater than its DHvap? (c) At a given temperature and pressure, how does the magnitude of the heat of vaporization of a substance compare with that of its heat of condensation?

Which forces are intramolecular and which intermolecular? (a) Those preventing oil from evaporating at room temperature (b) Those preventing butter from melting in a refrigerator (c) Those allowing silver to tarnish (d) Those preventing O2 in air from forming O atoms

Which forces are intramolecular and which intermolecular? (a) Those allowing fog to form on a cool, humid evening (b) Those allowing water to form when H2 is sparked (c) Those allowing liquid benzene to crystallize when cooled (d) Those responsible for the low boiling point of hexane

Name the phase change in each of these events: (a) Dew appears on a lawn in the morning. (b) Icicles change into liquid water. (c) Wet clothes dry on a summer day.

Name the phase change in each of these events: (a) A diamond film forms on a surface from gaseous carbon atoms in a vacuum. (b) Mothballs in a bureau drawer disappear over time. (c) Molten iron from a blast furnace is cast into ingots (pigs).

Liquid propane, a widely used fuel, is produced by compressing gaseous propane. During the process, approximately 15 kJ of energy is released for each mole of gas liquefied. Where does this energy come from?

Many heat-sensitive and oxygen-sensitive solids, such as camphor, are purified by warming under vacuum. The solid vaporizes directly, and the vapor crystallizes on a cool surface. What phase changes are involved in this method?

Describe the changes (if any) in potential energy and in kinetic energy among the molecules when gaseous PCl3 condenses to a liquid at a fixed temperature.

When benzene is at its melting point, two processes occur simultaneously and balance each other. Describe these processes on the macroscopic and molecular levels.

Liquid hexane (bp 5 698C) is placed in a closed container at room temperature. At first, the pressure of the vapor phase increases, but after a short time, it stops changing. Why?

Explain the effect of strong intermolecular forces on each of these parameters: (a) critical temperature; (b) boiling point; (c) vapor pressure; (d) heat of vaporization.

Match each numbered point in the phase diagram for compound Q with the correct molecular scene below: A B C D T 3 1 2 P

A liquid is in equilibrium with its vapor in a closed vessel at a fixed temperature. The vessel is connected by a stopcock to an evacuated vessel. When the stopcock is opened, will the final pressure of the vapor be different from the initial value if (a) some liquid remains; (b) all the liquid is first removed? Explain.

The phase diagram for substance A has a solid-liquid line with a positive slope, and that for substance B has a solid-liquid line with a negative slope. What macroscopic property can distinguish A from B?

Why does water vapor at 1008C cause a more severe burn than liquid water at 1008C?

From the data below, calculate the total heat (in J) needed to convert 22.00 g of ice at 26.008C to liquid water at 0.5008C: mp at 1 atm: 0.08C DH8 fus: 6.02 kJ/mol cliquid: 4.21 J/g?8C csolid: 2.09 J/g?8C

From the data below, calculate the total heat (in J) needed to convert 0.333 mol of gaseous ethanol at 3008C and 1 atm to liquid ethanol at 25.08C and 1 atm: bp at 1 atm: 78.58C DH8 vap: 40.5 kJ/mol cgas: 1.43 J/g?8C cliquid: 2.45 J/g?8C

A liquid has a DH8 vap of 35.5 kJ/mol and a boiling point of 1228C at 1.00 atm. What is its vapor pressure at 1138C?

Diethyl ether has a DH8 vap of 29.1 kJ/mol and a vapor pressure of 0.703 atm at 25.08C. What is its vapor pressure at 95.08C?

What is the DH 8 vap of a liquid that has a vapor pressure of 621 torr at 85.28C and a boiling point of 95.68C at 1 atm?

Methane (CH4) has a boiling point of 21648C at 1 atm and a vapor pressure of 42.8 atm at 21008C. What is the heat of vaporization of CH4?

Use these data to draw a qualitative phase diagram for ethylene (C2H4). Is C2H4(s) more or less dense than C2H4(l)? bp at 1 atm: 2103.78C mp at 1 atm: 2169.168C Critical point: 9.98C and 50.5 atm Triple point: 2169.178C and 1.2031023 atm

Use these data to draw a qualitative phase diagram for H2. Does H2 sublime at 0.05 atm? Explain. mp at 1 atm: 13.96 K bp at 1 atm: 20.39 K Triple point: 13.95 K and 0.07 atm Critical point: 33.2 K and 13.0 atm Vapor pressure of solid at 10 K: 0.001 atm

The phase diagram for sulfur is shown below. (a) Give a set of conditions under which it is possible to sublime the rhombic form of solid sulfur. (b) Describe the phase changes that a sample of sulfur undergoes at 1 atm when it is heated from 908C to 4508C. 1.0 GAS 95.4 114 119 445 SOLID LIQUID (rhombic) SOLID (monoclinic) T (C) P(atm) 5104 110

The phase diagram for xenon is shown below. (a) What phase is xenon in at room temperature and pressure? (b) Describe the phase changes that a sample of xenon undergoes at 21158C as it is compressed from 0.5 atm to 25 atm. (The critical pressure of xenon is 58 atm.) 125 121 120 115 0 112 110 108 105 SOLID 0.37 0.5 1.0 GAS T (C)

Sulfur dioxide is produced in enormous amounts for sulfuric acid production. It melts at 2738C and boils at 210.8C. Its DH8 fus is 8.619 kJ/mol and its DH8 vap is 25.73 kJ/mol. The specific heat capacities of the liquid and gas are 0.995 J/g?K and 0.622 J/g?K, respectively. How much heat is required to convert 2.500 kg of solid SO2 at the melting point to a gas at 60.8C?

Butane is a common fuel used in cigarette lighters and camping stoves. Normally supplied in metal containers under pressure, the fuel exists as a mixture of liquid and gas, so high temperatures may cause the container to explode. At 25.08C, the vapor pressure of butane is 2.3 atm. What is the pressure in the container at 1358C (DH8 vap 5 24.3 kJ/mol)?

Use Figure 12.10, p. 466, to answer the following: (a) Carbon dioxide is sold in steel cylinders under pressures of approximately 20 atm. Is there liquid CO2 in the cylinder at room temperature (208C)? At 408C? At 2408C? At 21208C? (b) Carbon dioxide is also sold as solid chunks, called dry ice, in insulated containers. If the chunks are warmed by leaving them in an open container at room temperature, will they melt? (c) If a container is nearly filled with dry ice and then sealed and warmed to room temperature, will the dry ice melt? (d) If dry ice is compressed at a temperature below its triple point, will it melt?

Why are covalent bonds typically much stronger than intermolecular forces?

(a) Name the type of force depicted in each scene below. (b) Rank the forces in order of increasing strength. C D A Cl C O O H + N S B

Oxygen and selenium are members of Group 6A(16). Water forms H bonds, but H2Se does not. Explain.

In solid I2, is the distance between the two I nuclei of one I2 molecule longer or shorter than the distance between two I nuclei of adjacent I2 molecules? Explain.

Polar molecules exhibit dipole-dipole forces. Do they also exhibit dispersion forces? Explain.

Distinguish between polarizability and polarity. How does each influence intermolecular forces?

How can one nonpolar molecule induce a dipole in a nearby nonpolar molecule?

What is the strongest interparticle force in each substance? (a) CH3OH (b) CCl4 (c) Cl2

What is the strongest interparticle force in each substance? (a) H3PO4 (b) SO2 (c) MgCl2

What is the strongest interparticle force in each substance? (a) CH3Cl (b) CH3CH3 (c) NH3

What is the strongest interparticle force in each substance? (a) Kr (b) BrF (c) H2SO4

Which member of each pair of compounds forms intermolecular H bonds? Draw the H-bonded structures in each case: (a) CH3CHCH3 or CH3SCH3 OH (b) HF or HBr

Which member of each pair of compounds forms intermolecular H bonds? Draw the H-bonded structures in each case: (a) (CH3)2NH or (CH3)3N (b) HOCH2CH2OH or FCH2CH2F

Which forces oppose vaporization of each substance? (a) Hexane (b) Water (c) SiCl4

Which forces oppose vaporization of each substance? (a) Br2 (b) SbH3 (c) CH3NH2

Which has the greater polarizability? Explain. (a) Br2 or I2 (b) CH2CH2 or CH3CH3 (c) H2O or H2Se

Which has the greater polarizability? Explain. (a) Ca21 or Ca (b) CH3CH3 or CH3CH2CH3 (c) CCl4 or CF4

Which member in each pair of liquids has the higher vapor pressure at a given temperature? Explain. (a) C2H6 or C4H10 (b) CH3CH2OH or CH3CH2F (c) NH3 or PH3

Which member in each pair of liquids has the lower vapor pressure at a given temperature? Explain. (a) HOCH2CH2OH or CH3CH2CH2OH (b) CH3COOH or (CH3)2CO (c) HF or HCl

Which substance has the lower boiling point? Explain. (a) LiCl or HCl (b) NH3 or PH3 (c) Xe or I2

Which substance has the higher boiling point? Explain. (a) CH3CH2OH or CH3CH2CH3 (b) NO or N2 (c) H2S or H2Te

Which substance has the lower boiling point? Explain. (a) CH3CH2CH2CH3 or CH2 CH2 CH2 CH2 (b) NaBr or PBr3 (c) H2O or HBr

Which substance has the higher boiling point? Explain. (a) CH3OH or CH3CH3 (b) FNO or ClNO (c) C F H F H C or C H F F H C

For pairs of molecules in the gas phase, average H-bond dissociation energies are 17 kJ/mol for NH3, 22 kJ/mol for H2O, and 29 kJ/mol for HF. Explain this increase in H-bond strength.

Dispersion forces are the only intermolecular forces present in motor oil, yet it has a high boiling point. Explain.

Why does the antifreeze ingredient ethylene glycol (HOCH2CH2OH; } 5 62.07 g/mol) have a boiling point of 197.68C, whereas propanol (CH3CH2CH2OH; } 5 60.09 g/mol), a compound with a similar molar mass, has a boiling point of only 97.48C?

Before the phenomenon of surface tension was understood, physicists described the surface of water as being covered with a skin. What causes this skinlike phenomenon?

Small, equal-sized drops of oil, water, and mercury lie on a waxed floor. How does each liquid behave? Explain.

Why does an aqueous solution of ethanol (CH3CH2OH) have a lower surface tension than water?

Why are units of energy per area (J/m2) used for surface tension values?

Does the strength of the intermolecular forces in a liquid change as the liquid is heated? Explain. Why does liquid viscosity decrease with rising temperature?

Rank the following in order of increasing surface tension at a given temperature, and explain your ranking: (a) CH3CH2CH2OH (b) HOCH2CH(OH)CH2OH (c) HOCH2CH2OH

Rank the following in order of decreasing surface tension at a given temperature, and explain your ranking: (a) CH3OH (b) CH3CH3 (c) H2CO

Rank the compounds in Problem 12.63 in order of decreasing viscosity at a given temperature; explain your ranking.

Rank the compounds in Problem 12.64 in order of increasing viscosity at a given temperature; explain your ranking.

Soil vapor extraction (SVE) is used to remove volatile organic pollutants, such as chlorinated solvents, from soil at hazardous waste sites. Vent wells are drilled, and a vacuum pump is applied to the subsurface. (a) How does this remove pollutants? (b) Why does heating combined with SVE speed the process?

Use Figure 12.2, p. 457 to answer the following: (a) Does it take more heat to melt 12.0 g of CH4 or 12.0 g of Hg? (b) Does it take more heat to vaporize 12.0 g of CH4 or 12.0 g of Hg? (c) What is the principal intermolecular force in each sample?

Pentanol (C5H11OH; } 5 88.15 g/mol) has nearly the same molar mass as hexane (C6H14; } 5 86.17 g/mol) but is more than 12 times as viscous at 208C. Explain.

For what types of substances is water a good solvent? For what types is it a poor solvent? Explain.

A water molecule can engage in as many as four H bonds. Explain

Warm-blooded animals have a narrow range of body temperature because their bodies have a high water content. Explain.

What property of water keeps plant debris on the surface of lakes and ponds? What is the ecological significance of this?

A drooping plant can be made upright by watering the ground around it. Explain.

Describe the molecular basis of the property of water responsible for the presence of ice on the surface of a frozen lake.

Describe in molecular terms what occurs when ice melts.

What is the difference between an amorphous solid and a crystalline solid on the macroscopic and molecular levels? Give an example of each.

How are a solids unit cell and crystal structure related?

For structures consisting of identical atoms, how many atoms are contained in the simple, body-centered, and facecentered cubic unit cells? Explain how you obtained the values.

An element has a crystal structure in which the width of the cubic unit cell equals the diameter of an atom. What type of unit cell does it have?

What specific difference in the positioning of spheres gives a crystal structure based on the face-centered cubic unit cell less empty space than one based on the body-centered cubic unit cell?

Both solid Kr and solid Cu consist of individual atoms. Why do their physical properties differ so much?

What is the energy gap in band theory? Compare its size in superconductors, conductors, semiconductors, and insulators.

Predict the effect (if any) of an increase in temperature on the electrical conductivity of (a) a conductor; (b) a semiconductor; (c) an insulator.

Besides the type of unit cell, what information is needed to find the density of a solid consisting of identical atoms?

What type of crystal lattice does each metal form? (The number of atoms per unit cell is given in parentheses.) (a) Ni (4) (b) Cr (2) (c) Ca (4)

What is the number of atoms per unit cell for each metal? (a) Polonium, Po (b) Manganese, Mn (c) Silver, Ag

Calcium crystallizes through cubic closest packing. If the atomic radius of calcium is 197 pm, find the density of the solid.

Chromium adopts the body-centered cubic unit cell in its crystal structure. If the density of chromium is 7.14 g/cm3, find its atomic radius.

When cadmium oxide reacts to form cadmium selenide, a change in unit cell occurs, as depicted below: A B O2 Se2 Cd2+ Cd2+ (a) What is the change in unit cell? (b) Does the coordination number of cadmium change? Explain.

As molten iron cools to 1674 K, it adopts one type of cubic unit cell; then, as the temperature drops below 1181 K, it changes to another, as depicted below: A B (a) What is the change in unit cell? (b) Which crystal structure has the greater packing efficiency?

Potassium adopts the body-centered cubic unit cell in its crystal structure. If the atomic radius of potassium is 227 pm, find the edge length of the unit cell.

Lead adopts the face-centered cubic unit cell in its crystal structure. If the edge length of the unit cell is 495 pm, find the atomic radius of lead.

Of the five major types of crystalline solid, which does each of the following form, and why: (a) Ni; (b) F2; (c) CH3OH; (d) Sn; (e) Si; (f) Xe?

Of the five major types of crystalline solid, which does each of the following form, and why: (a) SiC; (b) Na2SO4; (c) SF6; (d) cholesterol (C27H45OH); (e) KCl; (f) BN?

Zinc oxide adopts the zinc blende crystal structure (Figure P12.96). How many Zn21 ions are in the ZnO unit cell?

Calcium sulfide adopts the sodium chloride crystal structure (Figure P12.97). How many S22 ions are in the CaS unit cell? O2 Zn2+ S2 Ca2+ Figure P12.96 Figure P12.97

Zinc selenide (ZnSe) crystallizes in the zinc blende structure (see Figure P12.96) and has a density of 5.42 g/cm3. (a) How many Zn and Se ions are in each unit cell? (b) What is the mass of a unit cell? (c) What is the volume of a unit cell? (d) What is the edge length of a unit cell?

An element crystallizes in a face-centered cubic lattice and it has a density of 1.45 g/cm3 . The edge of its unit cell is 4.5231028 cm. (a) How many atoms are in each unit cell? (b) What is the volume of a unit cell? (c) What is the mass of a unit cell? (d) Calculate an approximate atomic mass for the element.

Classify each of the following as a conductor, insulator, or semiconductor: (a) phosphorus; (b) mercury; (c) germanium.

Classify each of the following as a conductor, insulator, or semiconductor: (a) carbon (graphite); (b) sulfur; (c) platinum.

Predict the effect (if any) of an increase in temperature on the electrical conductivity of (a) antimony; (b) tellurium; (c) bismuth.

Predict the effect (if any) of a decrease in temperature on the electrical conductivity of (a) silicon; (b) lead; (c) germanium.

Polonium, the Period 6 member of Group 6A(16), is a rare radioactive metal that is the only element with a crystal structure based on the simple cubic unit cell. If its density is 9.142 g/cm3, calculate an approximate atomic radius for polonium.

The coinage metalscopper, silver, and goldcrystallize in a cubic closest packed structure. Use the density of copper (8.95 g/cm3) and its molar mass (63.55 g/mol) to calculate an approximate atomic radius for copper.

One of the most important enzymes in the world nitrogenase, the plant protein that catalyzes nitrogen fixation contains active clusters of iron, sulfur, and molybdenum atoms. Crystalline molybdenum (Mo) has a body-centered cubic unit cell (d of Mo 5 10.28 g/cm3). (a) Determine the edge length of the unit cell. (b) Calculate the atomic radius of Mo.

Tantalum (Ta; d 5 16.634 g/cm3 and } 5 180.9479 g/mol) has a body-centered cubic structure with a unit-cell edge length of 3.3058 . Use these data to calculate Avogadros number.

When tin is added to copper, the resulting alloy (bronze) is much harder than copper. Explain.

In the process of doping a semiconductor, certain impurities are added to increase the electrical conductivity. Explain this process for an n-type and a p-type semiconductor.

State two molecular characteristics of substances that typically form liquid crystals. How is each related to function?

Distinguish between isotropic and anisotropic substances. To which category do liquid crystals belong?

How are the properties of high-tech ceramics the same as those of traditional clay ceramics, and how are they different? Refer to specific substances in your answer.

Why is the average molar mass of a polymer sample different from the molar mass of an individual chain?

How does the random coil shape relate to the radius of gyration of a polymer chain?

What factor(s) influence the viscosity of a polymer solution? What factor(s) influence the viscosity of a molten polymer? What is a polymer glass?

Use an example to show how branching and crosslinking can affect the physical behavior of a polymer.

Silicon and germanium are both semiconducting elements from Group 4A(14) that can be doped to improve their conductivity. Would each of the following form an n-type or a p-type semiconductor: (a) Ge doped with P; (b) Si doped with In?

Would each of the following form an n-type or a p-type semiconductor: (a) Ge doped with As; (b) Si doped with B?

The repeat unit in a polystyrene coffee cup has the formula C6H5CHCH2. If the molar mass of the polymer is 3.53105 g/mol, what is the degree of polymerization?

The monomer of poly(vinyl chloride) has the formula C2H3Cl. If there are 1565 repeat units in a single chain of the polymer, what is the molecular mass (in amu) of that chain?

The polypropylene (repeat unit CH3CHCH2) in a plastic toy has a molar mass of 2.83105 g/mol and a repeat unit length of 0.252 pm. Calculate the radius of gyration.

The polymer that is used to make 2-L soda bottles [poly(ethylene terephthalate)] has a repeat unit with molecular formula C10H8O4 and length 1.075 nm. Calculate the radius of gyration of a chain with a molar mass of 2.303104 g/mol.

A 0.75-L bottle is cleaned, dried, and closed in a room where the air is 228C and has 44% relative humidity (that is, the water vapor in the air is 0.44 of the equilibrium vapor pressure at 228C). The bottle is then brought outside and stored at 0.08C. (a) What mass of liquid water condenses inside the bottle? (b) Would liquid water condense at 108C? (See Table 5.2, p. 220.)

In an experiment, 5.00 L of N2 is saturated with water vapor at 228C and then compressed to half its volume at constant T. (a) What is the partial pressure of H2O in the compressed gas mixture? (b) What mass of water vapor condenses to liquid?

Barium is the largest nonradioactive alkaline earth metal. It has a body-centered cubic unit cell and a density of 3.62 g/cm3. What is the atomic radius of barium? (Volume of a sphere: V 5 4 3pr3 .)

Two important characteristics used to evaluate the risk of fire or explosion are a compounds lower flammable limit (LFL) and flash point. The LFL is the minimum percentage by volume in air that is ignitable. Below that, the mixture is too lean to burn. The flash point is the temperature at which the air over a confined liquid becomes ignitable. n-Hexane boils at 68.78C at 1 atm. At 20.08C, its vapor pressure is 121 mmHg. The LFL of n-hexane is 1.1%. Calculate the flash point of n-hexane.

Bismuth is used to calibrate instruments employed in high-pressure studies because it has several well-characterized crystalline phases. Its phase diagram (right) shows the liquid phase and five solid phases that are stable above 1 katm (1000 atm) and up to 3008C. (a) Which solid phases are stable at 258C? (b) Which phase is stable at 50 katm and 1758C? (c) As the pressure is reduced from 100 to 1 katm at 2008C, what phase transitions does bismuth undergo? (d) What phases are present at each of the triple points? Pressure (katm) 100 50 1 Temperature (C) 0 100 200 300 V III IV II Liquid

In making computer chips, a 4.00-kg cylindrical ingot of ultrapure n-type doped silicon that is 5.20 inches in diameter is sliced into wafers 1.1231024 m thick. (a) Assuming no waste, how many wafers can be made? (b) What is the mass of a wafer (d of Si 5 2.34 g/cm3; V of a cylinder 5 pr2h)? (c) A key step in making p-n junctions for the chip is chemical removal of the oxide layer on the wafer through treatment with gaseous HF. Write a balanced equation for this reaction. (d) If 0.750% of the Si atoms are removed during the treatment in part (c), how many moles of HF are required per wafer, assuming 100% reaction yield?

Methyl salicylate, C8H8O3, the odorous constituent of oil of wintergreen, has a vapor pressure of 1.00 torr at 54.38C and 10.0 torr at 95.38C. (a) What is its vapor pressure at 258C? (b) What is the minimum number of liters of air that must pass over a sample of the compound at 258C to vaporize 1.0 mg of it?

Mercury (Hg) vapor is toxic and readily absorbed from the lungs. At 20.8C, mercury (DHvap 5 59.1 kJ/mol) has a vapor pressure of 1.2031023 torr, which is high enough to be hazardous. To reduce the danger to workers in processing plants, Hg is cooled to lower its vapor pressure. At what temperature would the vapor pressure of Hg be at the safer level of 5.031025 torr?

Polytetrafluoroethylene (Teflon) has a repeat unit with the formula F2CCF2. A sample of the polymer consists of fractions with the following distribution of chains: Average no. Amount (mol) Fraction of Repeat Units of Polymer 1 273 0.10 2 330 0.40 3 368 1.00 4 483 0.70 5 525 0.30 6 575 0.10 (a) Determine the molar mass of each fraction. (b) Determine the number-average molar mass of the sample. (c) Another type of average molar mass of a polymer sample is called the weight-average molar mass, }w: }w 5 S (} of fraction 3 mass of fraction) total mass of all fractions Calculate the weight-average molar mass of the above sample.

A greenhouse contains 256 m3 of air at a temperature of 268C, and a humidifier in it vaporizes 4.20 L of water. (a) What is the pressure of water vapor in the greenhouse, assuming that none escapes and that the air was originally completely dry (d of H2O 5 1.00 g/mL)? (b) What total volume of liquid water would have to be vaporized to saturate the air (that is, achieve 100% relative humidity)? (See Table 5.2, p. 220.)

Like most transition metals, tantalum (Ta) exhibits several oxidation states. Give the formula of each tantalum compound whose unit cell is depicted below: (a) (b) Ta Ta N C C

KF has the same type of crystal structure as NaCl. The unit cell of KF has an edge length of 5.39 . Find the density of KF.

Furfural, which is prepared from corncobs, is an important solvent in synthetic rubber manufacturing, and it is reduced to furfuryl alcohol, which is used to make polymer resins. Furfural can also be oxidized to 2-furoic acid. furfuryl alcohol furfural 2-furoic acid (a) Which of these compounds can form H bonds? Draw structures in each case. (b) The molecules of some substances can form an internal H bond, that is, an H bond within a molecule. This takes the form of a polygon with atoms as corners and bonds as sides and an H bond as one of the sides. Which of these molecules is (are) likely to form a stable internal H bond? Draw the structure. (Hint: Structures with 5 or 6 atoms as corners are most stable.)

On a humid day in New Orleans, the temperature is 22.08C, and the partial pressure of water vapor in the air is 31.0 torr. The 9000-ton air-conditioning system in the Louisiana Superdome maintains an inside air temperature of 22.08C also, but a partial pressure of water vapor of 10.0 torr. The volume of air in the dome is 2.43106 m3, and the total pressure is 1.0 atm both inside and outside the dome. (a) What mass of water (in metric tons) must be removed every time the inside air is completely replaced with outside air? (Hint: How many moles of gas are in the dome? How many moles of water vapor? How many moles of dry air? How many moles of outside air must be added to the air in the dome to simulate the composition of outside air?) (b) Find the heat released when this mass of water condenses.

The boiling point of amphetamine, C9H13N, is 2018C at 760 torr and 838C at 13 torr. What is the concentration (in g/m3) of amphetamine when it is in contact with 20.8C air?

Diamond has a face-centered cubic unit cell, with four more C atoms in tetrahedral holes within the cell. Densities of diamonds vary from 3.01 g/cm3 to 3.52 g/cm3 because C atoms are missing from some holes. (a) Calculate the unit-cell edge length of the densest diamond. (b) Assuming the cell dimensions are fixed, how many C atoms are in the unit cell of the diamond with the lowest density?

Is it possible for a salt of formula AB3 to have a facecentered cubic unit cell of anions with cations in all eight of the available holes? Explain.

The density of solid gallium at its melting point is 5.9 g/cm3, whereas that of liquid gallium is 6.1 g/cm3. Is the temperature at the triple point higher or lower than the normal melting point? Is the slope of the solid-liquid line for gallium positive or negative?

A 4.7-L sealed bottle containing 0.33 g of liquid ethanol, C2H6O, is placed in a refrigerator and reaches equilibrium with its vapor at 2118C. (a) What mass of ethanol is present in the vapor? (b) When the container is removed and warmed to room temperature, 20.8C, will all the ethanol vaporize? (c) How much liquid ethanol would be present at 0.08C? The vapor pressure of ethanol is 10. torr at 22.38C and 40. torr at 198C.

Substance A has the following properties. mp at 1 atm: 220.8C bp at 1 atm: 858C DHfus: 180. J/g DHvap: 500. J/g csolid: 1.0 J/g?8C cliquid: 2.5 J/g?8C cgas: 0.5 J/g?8C At 1 atm, a 25-g sample of A is heated from 240.8C to 100.8C at a constant rate of 450. J/min. (a) How many minutes does it take to heat the sample to its melting point? (b) How many minutes does it take to melt the sample? (c) Perform any other necessary calculations, and draw a curve of temperature vs. time for the entire heating process.

An aerospace manufacturer is building a prototype experimental aircraft that cannot be detected by radar. Boron nitride is chosen for incorporation into the body parts, and the boric acid/ ammonia method is used to prepare the ceramic material. Given 85.5% and 86.8% yields for the two reaction steps, how much boron nitride can be prepared from 1.00 metric ton of boric acid and 12.5 m3 of ammonia at 275 K and 3.073103 kPa? Assume that ammonia does not behave ideally under these conditions and is recycled completely in the reaction process.

The ball-and-stick models below represent three compounds with the same molecular formula, C4H8O2: A C B (a) Which compound(s) can form intermolecular H bonds? (b) Which has the highest viscosity?

The DH8 f of gaseous dimethyl ether (CH3OCH3) is 2185.4 kJ/mol; the vapor pressure is 1.00 atm at 223.78C and 0.526 atm at 237.88C. (a) Calculate DH8 vap of dimethyl ether. (b) Calculate DH8 f of liquid dimethyl ether.

The crystal structure of sodium is based on the bodycentered cubic unit cell. What is the mass of one unit cell of Na?

The intrinsic viscosity of a polymer solute in a solvent, [h]solvent, is the portion of the total viscosity due to the solute and is related to solute shape. It has also been found to relate to intermolecular interactions between solvent and polymer: higher [h]solvent means stronger interaction. The [h]solvent values of polymers in solution are given by the Mark-Houwink equation, [h]solvent 5 K}a, where } is the molar mass of the polymer and K and a are constants specific to the polymer and solvent. Use the data below for substances at 258C to answer the following questions: (a) A polystyrene sample has a molar mass of 104,160 g/mol. Calculate the intrinsic viscosity in benzene and in cyclohexane. Which solvent has stronger interactions with the polymer? (b) A different polystyrene sample has a molar mass of 52,000 g/mol. Calculate its [h]benzene. Given a polymer standard of known }, how could you use its measured [h] in a given solvent to determine the molar mass of any sample of that polymer? (c) Compare [h] of a polyisobutylene sample [repeat unit (CH3)2CCH2] with a molar mass of 104,160 g/mol with that of the polystyrene in part (a). What does this suggest about the solventpolymer interactions of the two samples?

One way of purifying gaseous H2 is to pass it under high pressure through the holes of a metals crystal structure. Palladium, which adopts a cubic closest packed structure, absorbs more H2 than any other element and is one of the metals used for this purpose. How the metal and H2 interact is unclear, but it is estimated that the density of absorbed H2 approaches that of liquid hydrogen (70.8 g/L). What volume (in L) of gaseous H2 (at STP) can be packed into the spaces of 1 dm3 of palladium metal?