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1 Million+ Step-by-step solutionsmath books Q:Describe the intermolecular forces that must be overcome to convertDescribe the intermolecular forces that must be overcome to convert these substances from a liquid to a gas:
(a) SO2,
(b) CH3COOH,
(c) H2S?
Q:Which type of intermolecular force accounts for each of theseWhich type of intermolecular force accounts for each of these differences:
(a) CH3OH boils at 65 oC; CH3SH boils at 6 oC.
(b) Xe is liquid at atmospheric pressure and 120 K, whereas Ar is a gas under the same conditions.
(c) Kr, atomic weight 84, boils at 120.9 K, whereas Cl2, molecular weight about 71, boils at 238 K.
(d) Acetone boils at 56 oC, whereas 2-methylpropane boils at – 12oC.
Which type of intermolecular force accounts for each of theseWhich type of intermolecular force accounts for each of theseQ:(a) What is meant by the term polarizability? (b)Which of the(a) What is meant by the term polarizability?
(b)Which of the following atoms would you expect to be most polarizable: N, P, As, Sb? Explain.
(c) Put the following molecules in order of increasing polarizability: GeCl4, CH4, SiCl4, SiH4, and GeBr4.
(d) Predict the order of boiling points of the substances in part (c)?
Q:(a) Which kind of intermolecular attractive force is shown in(a) Which kind of intermolecular attractive force is shown in each case here?
(a) Which kind of intermolecular attractive force is shown in

(b) Predict which of the four interactions is the weakest?

Q:True or false: (a) For molecules with similar molecular weights, theTrue or false:
(a) For molecules with similar molecular weights, the dispersion forces become stronger as the molecules become more polarizable.
(b) For the noble gases the dispersion forces decrease while the boiling points increase as you go down the column in the periodic table.
(c) In terms of the total attractive forces for a given substance dipole-dipole interactions, when present, are always larger than dispersion forces.
(d) All other factors being the same, dispersion forces between linear molecules are greater than dispersion forces between molecules whose shapes are nearly spherical?
Q:Which member in each pair has the larger dispersion forces: (a)Which member in each pair has the larger dispersion forces:
(a) H2O or H2S,
(b) CO2 or CO,
(c) SiH4 or GeH4?
Q:Which member in each pair has the stronger intermolecular dispersionWhich member in each pair has the stronger intermolecular dispersion forces:
(a) Br2 or O2,
(b) CH3CH2CH2CH2SH or CH3CH2CH2CH2CH2SH,
(c) CH3CH2CH2Cl or (CH3)2CHCl?
Q:Butane and 2-methylpropane, whose space-filling models are shown at theButane and 2-methylpropane, whose space-filling models are shown at the top of the next column, are both nonpolar and have the same molecular formula, C4H10, yet butane has the higher boiling point (-0.5 °C compared to -11.7 °C). Explain.
Butane and 2-methylpropane, whose space-filling models are shown at theQ:Propyl alcohol (CH3CH2CH2OH) and isopropyl alcohol [(CH3)2CHOH], whose space-filling modelsPropyl alcohol (CH3CH2CH2OH) and isopropyl alcohol [(CH3)2CHOH], whose space-filling models are shown, have boiling points of 97.2 oC and 82.5 oC, respectively. Explain why the boiling point of propyl alcohol is higher, even though both have the molecular formula C3H8O.
Propyl alcohol (CH3CH2CH2OH) and isopropyl alcohol [(CH3)2CHOH], whose space-filling modelsQ:(a) What atoms must a molecule contain to participate in(a) What atoms must a molecule contain to participate in hydrogen bonding with other molecules of the same kind?
(b) Which of the following molecules can form hydrogen bonds with other molecules of the same kind: CH3F, CH3NH2, CH3OH, CH3Br?
Q:Rationalize the difference in boiling points in each pair: (a) HFRationalize the difference in boiling points in each pair:
(a) HF (20 oC) and HCl (- 85 oC),
(b) CHCl3 (61 oC) and CHBr3 (150 oC),
(c) Br2 (59 oC) and ICI (97 oC)?
Q:Ethylene glycol (HOCH2CH2OH), the major substance in antifreeze, has aEthylene glycol (HOCH2CH2OH), the major substance in antifreeze, has a normal boiling point of 198oC. By comparison, ethyl alcohol (CH3CH2OH) boils at 78oC at atmospheric pressure. Ethylene glycol dimethyl ether (CH3OCH2CH2OCH3) has a normal boiling point of 83 oC, and ethyl methyl ether (CH3CH2OCH3) has a normal boiling point of 11 oC.
(a) Explain why replacement of a hydrogen on the oxygen by a CH3 group generally results in a lower boiling point.
(b) What are the major factors responsible for the difference in boiling points of the two ethers?
Q:Identify the type or types of intermolecular forces present inIdentify the type or types of intermolecular forces present in each substance and then select the substance in each pair that has the higher boiling point:
(a) Propane C3H8 or n-butane C4H10,
(b) Diethyl ether CH3CH2OCH2CH3 or 1-butanol CH3CH2CH2CH2OH,
(c) Sulfur dioxide SO2 or sulfur trioxide SO3,
(d) Phosgene Cl2CO or formaldehyde H2CO?
Q:Look up and compare the normal boiling points and normalLook up and compare the normal boiling points and normal melting points of H2O and H2S.
(a) Based on these physical properties, which substance has stronger intermolecular forces? What kind of intermolecular forces exist for each molecule?
(b) Predict whether solid H2S is more or less dense than liquid H2S. How does this compare to H2O? Explain.
(c) Water has an unusually high specific heat. Is this related to its intermolecular forces? Explain.
Q:Do you expect the viscosity of glycerol, C3H5(OH)3, to beDo you expect the viscosity of glycerol, C3H5(OH)3, to be larger or smaller than that of 1-propanol, C3H7OH? Explain?
Do you expect the viscosity of glycerol, C3H5(OH)3, to beQ:The following quote about ammonia (NH3) is from a textbookThe following quote about ammonia (NH3) is from a textbook of inorganic chemistry: “It is estimated that 26% of the hydrogen bonding in NH3 breaks down on melting, 7% on warming from the melting to the boiling point, and the final 67% on transfer to the gas phase at the boiling point.” From the standpoint of the kinetic energy of the molecules, explain
(a) Why there is a decrease of hydrogen-bonding energy on melting and
(b) Why most of the loss in hydrogen bonding occurs in the transition from the liquid to the vapor state?
Q:A number of salts containing the tetrahedral polyatomic anion, BF4-A number of salts containing the tetrahedral polyatomic anion, BF4- , are ionic liquids, whereas salts containing the somewhat larger tetrahedral ion SO42- do not form ionic liquids?
Explain this observation.
Q:The generic structural formula for a 1-alkyl-3-methylimidazolium cation is Where RThe generic structural formula for a 1-alkyl-3-methylimidazolium cation is
The generic structural formula for a 1-alkyl-3-methylimidazolium cation is 
Where R

Where R is a ¬CH2(CH2)nCH3 alkyl group. The melting points of the salts that form between the 1-alkyl-3-methylimidazolium cation and the PF6- anion are as follows:
R = CH2CH3 (m.p. 60 °C), R CH2CH2CH3 (m.p. 40 °C),
R= CH2CH2CH2CH3 (m.p. 10 °C) and
R = CH2CH2CH2CH2CH2CH3(m.p. = – 61 oC). Why does the melting point decrease as the length of alkyl group increases?

Q:(a) Explain why surface tension and viscosity decrease with increasing(a) Explain why surface tension and viscosity decrease with increasing temperature.
(b) Why do substances with high surface tensions also tend to have high viscosities?
Q:(a) Distinguish between adhesive forces and cohesive forces. (b) What adhesive(a) Distinguish between adhesive forces and cohesive forces.
(b) What adhesive and cohesive forces are involved when a paper towel absorbs water? (c) Explain the cause for the U-shaped meniscus formed when water is in a glass tube?
Q:Explain the following observations: (a) The surface tension of CHBr3Explain the following observations:
(a) The surface tension of CHBr3 is greater than that of CHCl3.
(b) As temperature increases, oil flows faster through a narrow tube.
(c) Raindrops that collect on a waxed automobile hood take on a nearly spherical shape. (d) Oil droplets that collect on a waxed automobile hood take on a flat shape?
Q:Hydrazine (H2NNH2), hydrogen peroxide (HOOH), and water (H2O) all haveHydrazine (H2NNH2), hydrogen peroxide (HOOH), and water (H2O) all have exceptionally high surface tensions compared with other substances of comparable molecular weights.
(a) Draw the Lewis structures for these three compounds.
(b)What structural property do these substances have in common, and how might that account for the high surface tensions?
Q:The boiling points, surface tensions, and viscosities of water andThe boiling points, surface tensions, and viscosities of water and several alchohols are as follows:
The boiling points, surface tensions, and viscosities of water and

(a) For ethanol, propanol, and n-butanol the boiling points, surface tensions, and viscosities all increase. What is the reason for this increase?
(b) How do you explain the fact that propanol and ethylene glycol have similar molecular weights (60 versus 62 amu), yet the viscosity of ethylene glycol is more than 10 times larger than propanol?
(c) How do you explain the fact that water has the highest surface tension but the lowest viscosity?

Q:(a) Would you expect the viscosity of n-pentane, CH3CH2CH2CH2CH3, to(a) Would you expect the viscosity of n-pentane, CH3CH2CH2CH2CH3, to be larger or smaller than the viscosity of n-hexane (3.26 × 10-4kg/m-s)(from Table 11.4)?
(b) If you compared their viscosities at 270 K, would you expect the viscosity of neopentane, (CH3)4C, to be smaller or larger than n-pentane? (See Figure 11.6 to see the shapes of these molecules.)
Q:Name the phase transition in each of the following situationsName the phase transition in each of the following situations and indicate whether it is exothermic or endothermic:
(a) When ice is heated, it turns to water.
(b) Wet clothes dry on a warm summer day
(c) Frost appears on a window on a cold winter day
(d) Droplets of water appear on a cold glass of beer?
Q:If 42.0 kJ of heat is added to a 32.0-gIf 42.0 kJ of heat is added to a 32.0-g sample of liquid methane under 1 atm of pressure at a temperature of – 170 oC, what are the final state and temperature of the methane once the system equilibrates? Assume no heat is lost to the surroundings. The normal boiling point of methane is – 161.5 oC. The specific heats of liquid and gaseous methane are 3.48 and 2.22 J/g-K, respectively?
If 42.0 kJ of heat is added to a 32.0-gQ:Name the phase transition in each of the following situationsName the phase transition in each of the following situations and indicate whether it is exothermic or endothermic:
(a) Bromine vapor turns to bromine liquid as it is cooled.
(b) Crystals of iodine disappear from an evaporating dish as they stand in a fume hood.
(c) Rubbing alcohol in an open container slowly disappears.
(d) Molten lava from a volcano turns into solid rock?
Q:Explain why any substance’s heat of fusion is generally lowerExplain why any substance’s heat of fusion is generally lower than its heat of vaporization?
Q:Ethyl chloride (C2H5Cl) boils at 12 oC. When liquid C2H5ClEthyl chloride (C2H5Cl) boils at 12 oC. When liquid C2H5Cl under pressure is sprayed on a room-temperature (25 oC) surface in air, the surface is cooled considerably.
(a) What does this observation tell us about the specific heat of C2H5Cl(g) as compared with C2H5Cl(l)?
(b) Assume that the heat lost by the surface is gained by ethyl chloride. What enthalpies must you consider if you were to calculate the final temperature of the surface?
Q:For many years drinking water has been cooled in hotFor many years drinking water has been cooled in hot climates by evaporating it from the surfaces of canvas bags or porous clay pots. How many grams of water can be cooled from 35 oC to 20 oC by the evaporation of 60 g of water? (The heat of vaporization of water in this temperature range is 2.4 kj / g. The specific heat of water is 4.18 j/g – k)?
Q:Compounds like CCl2F2 are known as chlorofluorocarbons, or CFCs. TheseCompounds like CCl2F2 are known as chlorofluorocarbons, or CFCs. These compounds were once widely used as refrigerants but are now being replaced by compounds that are believed to be less harmful to the environment. The heat of vaporization of CCl2F2 is 289 j/g. What mass of this substance must evaporate to freeze 200 g of water initially at 15 oC? (The heat of fusion of water is 334 j/g; the specific heat of water is 4.18 j/g – k.)
Q:Ethanol (C2H5OH) melts a – 144 oC and boils atEthanol (C2H5OH) melts a – 144 oC and boils at 78 °C. The enthalpy of fusion of ethanol is 5.02 kj/mol, and its enthalpy of vaporization is 38.56 kj/mol. The specific heats of solid and liquid ethanol are 0.97j/g – k and 2.3 j/g – K, respectively.
(a) How much heat is required to convert 42.0 g of ethanol at 35 °C to the vapor phase at 78 °C?
(b) How much heat is required to convert the same amount of ethanol at – 155 oC to the vapor phase at 78 °C?
Q:The fluorocarbon compound C2Cl3F3 has a normal boiling point ofThe fluorocarbon compound C2Cl3F3 has a normal boiling point of 47.6 oC. The specific heats of C2Cl3F3(l) and C2Cl3F3(g) are 0.91 j/g – K and 0.67 j/g – K, respectively. The heat of vaporization for the compound is 27.49 kj/mol. Calculate the heat required to convert 35.0 g of C2Cl3F3 from a liquid at 10.00 °C to a gas at 105.00 °C?
Q:(a) What is the significance of the critical pressure of(a) What is the significance of the critical pressure of a substance?
(b) What happens to the critical temperature of a series of compounds as the force of attraction between molecules increases?
(c) Which of the substances listed in Table 11.5 can be liquefied at the temperature of liquid nitrogen (- 196 oC)?
Q:The critical temperature (K) and pressure (atm) of a seriesThe critical temperature (K) and pressure (atm) of a series of halogenated are as follows:
The critical temperature (K) and pressure (atm) of a series

(a) List the intermolecular forces that occur for each compound.
(b) Predict the order of increasing intermolecular attraction, from least to most, for this series of compounds.
(c) Predict the critical temperature and pressure for CCl4 based on the trends in this table. Look up the experimentally determined critical temperatures and pressures for CCl4, using a source such as the CRC Handbook of Chemistry and Physics, and suggest a reason for any discrepancies?

Q:Explain how each of the following affects the vapor pressureExplain how each of the following affects the vapor pressure of a liquid:
(a) Volume of the liquid,
(b) Surface area,
(c) Intermolecular attractive forces,
(d) Temperature,
(e) Density of the liquid.
Q:Using this graph of CS2 data, determine (a) the approximate vaporUsing this graph of CS2 data,
Using this graph of CS2 data, 
determine  
(a) the approximate vapor

determine
(a) the approximate vapor pressure of CS2 at 30 °C,
(b) the temperature at which the vapor pressure equals 300 torr,
(c) the normal boiling point of CS2?

Q:Acetone, H3CCOCH3, has a boiling point of 56 °C. BasedAcetone, H3CCOCH3, has a boiling point of 56 °C. Based on the data given in Figure 11.25, would you expect acetone to have a higher or lower vapor pressure than ethanol at 25 °C?
Q:(a) Place the following substances in order of increasing volatility:(a) Place the following substances in order of increasing volatility: CH4, CBr4, CH2Cl2, CH3Cl, CHBr3, and CH2Br2. Explain.
(b) How do the boiling points vary through this series?
Q:True or false: (a)CBr4 is more volatile than CCl4. (b)CBr4 has aTrue or false:
(a)CBr4 is more volatile than CCl4.
(b)CBr4 has a higher boiling point than CCl4.
(c)CBr4 has weaker intermolecular forces than CCl4.
(d)CBr4 has a higher vapor pressure at the same temperature than CCl4.
Q:(a) Two pans of water are on different burners of(a) Two pans of water are on different burners of a stove. One pan of water is boiling vigorously, while the other is boiling gently. What can be said about the temperature of the water in the two pans?
(b) A large container of water and a small one are at the same temperature. What can be said about the relative vapor pressures of the water in the two containers?
Q:Explain the following observations: (a) Water evaporates more quickly onExplain the following observations:
(a) Water evaporates more quickly on a hot, dry day than on a hot, humid day.
(b) It takes longer to cook an egg in boiling water at high altitudes than it does at lower altitudes?
Q:Using the vapor-pressure curves in Figure 11.25, (a) Estimate theUsing the vapor-pressure curves in Figure 11.25,
(a) Estimate the boiling point of ethanol at an external pressure of 200 torr;
(b) Estimate the external pressure at which ethanol will boil at 60 oC;
(c) Estimate the boiling point of diethyl ether at
(d) Estimate the external pressure at which diethyl ether will boil at 40 oC?
Q:Appendix B lists the vapor pressure of water at variousAppendix B lists the vapor pressure of water at various external pressures.
(a) Plot the data in Appendix B, vapor pressure (torr) versus temperature (oC). From your plot, estimate the vapor pressure of water at body temperature, 37 oC.
(b) Explain the significance of the data point at 760.0 torr, 100 oC.
(c) A city at an altitude of 5000 ft above sea level has a barometric pressure of 633 torr. To what temperature would you have to heat water to boil it in this city?
(d) A city at an altitude of 500 ft below sea level would have a barometric pressure of 774 torr. To what temperature would you have to heat water to boil it in this city?
(e) For the two cities in parts (c) and (d), compare the average kinetic energies of the water molecules at their boiling points. Are the kinetic energies the same or different?
Explain.
Q:(a) What is the significance of the critical point in(a) What is the significance of the critical point in a phase diagram?
(b) Why does the line that separates the gas and liquid phases end at the critical point?
Q:(a) What is the significance of the triple point in(a) What is the significance of the triple point in a phase diagram?
(b) Could you measure the triple point of water by measuring the temperature in a vessel in which water vapor, liquid water, and ice are in equilibrium under one atmosphere of air? Explain.
Q:Referring to Figure 11.28, describe all the phase changes thatReferring to Figure 11.28, describe all the phase changes that would occur in each of the following cases:
(a) Water vapor originally at 0.005 atm and – 0.5 oC is slowly compressed at constant temperature until the final pressure is 20 atm.
(b) Water originally at 100.0 oC and 0.50 atm is cooled at constant pressure until the temperature is – 10 oC?
Q:The molecules Have the same molecular formula (C3H8O) but different normalThe molecules
The molecules 
Have the same molecular formula (C3H8O) but different normal

Have the same molecular formula (C3H8O) but different normal boiling points, as shown. Rationalize the difference in boiling points?

Q:Referring to Figure 11.29, describe the phase changes (and theReferring to Figure 11.29, describe the phase changes (and the temperatures at which they occur) when CO2 is heated from – 80 oC to – 20 oC at
(a) A constant pressure of 3 atm,
(b) A constant pressure of 6 atm.
Q:The phase diagram for neon is Temperature (K) Use the phase diagramThe phase diagram for neon is
The phase diagram for neon is 
Temperature (K) 
Use the phase diagram

Temperature (K)
Use the phase diagram to answer the following questions.
(a) What is the approximate value of the normal melting point?
(b) Over what pressure range will solid neon sublime?
(c) At room temperature (T = 25 °C) can neon be liquefied by compressing it?

Q:Use the phase diagram of neon to answer the followingUse the phase diagram of neon to answer the following questions.
(a)What is the approximate value of the normal boiling point?
(b) What can you say about the strength of the intermolecular forces in neon and argon based on the critical points of Ne and Ar?
Q:The fact that water on Earth can readily be foundThe fact that water on Earth can readily be found in all three states (solid, liquid, and gas) is in part a consequence of the fact that the triple point of water (T = 0.01 °C, P = 0.006 atm) falls within a range of temperatures and pressures found on Earth. Saturn’s largest moon Titan has a considerable amount of methane in its atmosphere. The conditions on the surface of Titan are estimated to be P = 1.6 atm and T = – 178 oC. As seen from the phase diagram of methane (Figure 11.30), these conditions are not far from the triple point of methane, raising the tantalizing possibility that solid, liquid, and gaseous methane can be found on Titan.
(a)What state would you expect to find methane in on the surface of Titan?
(b) On moving upward through the atmosphere the pressure will decrease. If we assume that the temperature does not change, what phase change would you expect to see as we move away from the surface?
Q:At 25 °C gallium is a solid with a densityAt 25 °C gallium is a solid with a density of 5.19 g/cm3. Its melting point, 29.8 °C, is low enough that you can melt it by holding it in your hand. The density of liquid gallium just above the melting point is 6.1 g/cm3. Based on this information, what unusual feature would you expect to find in the phase diagram of gallium?
At 25 °C gallium is a solid with a densityQ:In terms of the arrangement and freedom of motion ofIn terms of the arrangement and freedom of motion of the molecules, how are the nematic liquid crystalline phase and an ordinary liquid phase similar? How are they different?
Q:What observations made by Reinitzer on cholesteryl benzoate suggested thatWhat observations made by Reinitzer on cholesteryl benzoate suggested that this substance possesses a liquid crystalline phase?
Q:One of the more effective liquid crystalline substances employed inOne of the more effective liquid crystalline substances employed in LCDs is the molecule
One of the more effective liquid crystalline substances employed in

(a) How many double bonds are there in this molecule?
(b) Describe the features of the molecule that make it prone to show liquid crystalline behavior?

Q:For a given substance, the liquid crystalline phase tends toFor a given substance, the liquid crystalline phase tends to be more viscous than the liquid phase. Why?
Q:The phase diagram of a hypothetical substance is (a) Estimate theThe phase diagram of a hypothetical substance is
The phase diagram of a hypothetical substance is 
(a) Estimate the

(a) Estimate the normal boiling point and freezing point of the substance.
(b) What is the physical state of the substance under the following conditions:
(i) T = 150 K, P = 0.2 atm, (ii) T = 100 K, P = 0.8 atm, (iii) T = 300 K, P = 1.0 atm?
(c) What is the triple point of the substance?

Q:Describe how a cholesteric liquid crystal phase differs from aDescribe how a cholesteric liquid crystal phase differs from a nematic phase?
Q:It often happens that a substance possessing a smectic liquidIt often happens that a substance possessing a smectic liquid crystalline phase just above the melting point passes into a nematic liquid crystalline phase at a higher temperature. Account for this type of behavior?
Q:The smectic liquid crystalline phase can be said to beThe smectic liquid crystalline phase can be said to be more highly ordered than the nematic phase. In what sense is this true?
Q:As the intermolecular attractive forces between molecules increase in magnitude,As the intermolecular attractive forces between molecules increase in magnitude, do you expect each of the following to increase or decrease in magnitude?
(a) Vapor pressure,
(b) Heat of vaporization,
(c) Boiling point,
(d) Freezing point,
(e) Viscosity,
(f) Surface tension,
(g) Critical temperature?
Q:Suppose you have two colorless molecular liquids, one boiling atSuppose you have two colorless molecular liquids, one boiling at – 84 oC, the other at 34 °C, and both at atmospheric pressure. Which of the following statements is correct? For each statement that is not correct, modify the statement so that it is correct.
(a) The higher-boiling liquid has greater total intermolecular forces than the lower-boiling liquid.
(b) The lower-boiling liquid must consist of nonpolar molecules.
(c) The lower-boiling liquid has a lower molecular weight than the higher-boiling liquid. (d) The two liquids have identical vapor pressures at their normal boiling points.
(e) At both liquids have vapor pressures of 760 mm Hg.
Q:Two isomers of the planar compound 1,2-dichloroethylene are shown here (a)Two isomers of the planar compound 1,2-dichloroethylene are shown here
Two isomers of the planar compound 1,2-dichloroethylene are shown here 
(a)

(a) Which of the two isomers will have the stronger dipole – dipole forces?
(b) One isomer has a boiling point of 60.3 °C and the other 47.5 °C. Which isomer has which boiling point?

Q:In dichloromethane, CH2Cl2, (µ = 1.60 D) the dispersion forceIn dichloromethane, CH2Cl2, (µ = 1.60 D) the dispersion force contribution to the intermolecular attractive forces is about five times larger than the dipole-dipole contribution. Compared to CH2Cl2, would you expect the relative importance of the dipole-dipole contribution to increase or decrease
(a) In dibromomethane (µ = 1.43 D),
(b) In difluoromethane (µ = 1.93 D)? Explain.
Q:When an atom or group of atoms is substituted forWhen an atom or group of atoms is substituted for an H atom I benzene (C6H6), the boiling point changes. Explain the order of the following boiling points:
C6H6 (80 oC), C6H5CI (132 oC), C6H5Br (156 oC), C6H5OH (182 oC)?
Q:The DNA double helix (Figure 24.30) at the atomic levelThe DNA double helix (Figure 24.30) at the atomic level looks like a twisted ladder, where the “rungs” of the ladder consist of molecules that are hydrogen-bonded together. Sugar and phosphate groups make up the sides of the ladder. Shown are the structures of the adenine-thymine (AT) “base pair” and the guanine-cytosine (GC) base pair:
The DNA double helix (Figure 24.30) at the atomic levelThe DNA double helix (Figure 24.30) at the atomic level

You can see that AT base pairs are held together by two hydrogen bonds, and the GC base pairs are held together by three hydrogen bonds. Which base pair is more stable to heating? Why?

Q:At three different temperatures T1, T2 and T3, the moleculesAt three different temperatures T1, T2 and T3, the molecules in a liquid crystal align in these ways:
At three different temperatures T1, T2 and T3, the molecules

(a) At which temperature or temperatures is the substance in a liquid crystalline state?
at those temperature, which type of liquid crystalline phase is depicted?
(b) Which is the highest of the three temperature?

Q:Use the normal boiling points Propane, C3H8, – 42.1 oC Butane, C4H10,Use the normal boiling points
Propane, C3H8, – 42.1 oC
Butane, C4H10, – 0.5 oC
Pentane, C5H12, 36.1 oC
Hexane, C6H14, 68.7 oC
Heptane, C7H16, 98.4 oC
To estimate the normal boiling point of octane, C8H18. Explain the trend in the boiling point.
Q:One of the attractive features of ionic liquids is theirOne of the attractive features of ionic liquids is their low vapor pressure, which in turn tends to make them nonflammable. Why do you think ionic liquids have lower vapor pressures than most room-temperature molecular liquids?
Q:(a) When you exercise vigorously, you sweat. How does this(a) When you exercise vigorously, you sweat. How does this help your body cool?
(b) A flask of water is connected to a vacuum pump. A few moments after the pump is turned on, the water begins to boil. After a few minutes, the water begins to freeze. Explain why these processes occur.
Q:The following table gives the vapor pressure of hexafluorobenzene (C6F6)The following table gives the vapor pressure of hexafluorobenzene (C6F6) as a function of temperature:
The following table gives the vapor pressure of hexafluorobenzene (C6F6)

(a) By plotting these data in a suitable fashion, determine whether the Clausius-Clapeyron equation (Equation 11.1) is obeyed. If it is obeyed, use your plot to determine
(Hvap for C6F6.
(b) Use these data to determine the boiling point of the compound.

Q:Suppose the vapor pressure of a substance is measured atSuppose the vapor pressure of a substance is measured at two different temperatures.
(a) By using the Clausius-Clapeyron equation (Equation 11.1) derive the following relationship between the vapor pressures, P1 and P2, and the absolute temperatures at which they were measured, T1 and T2:
Suppose the vapor pressure of a substance is measured at

(b) Gasoline is a mixture of

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