Chapter Ten Liquids and Solids

Copyright © Houghton Mifflin Company. All rights reserved.10 | 2 Question Which one of the following is the strongest intermolecular force experienced by noble gases? a)London dispersion forces b)Dipole–dipole interactions c)Hydrogen bonding d)Ion–ion interactions

Copyright © Houghton Mifflin Company. All rights reserved.10 | 3 Answer a)London dispersion forces Section 10.1, Intermolecular Forces Noble gases are nonpolar, so their only intermolecular forces are London dispersion forces.

Copyright © Houghton Mifflin Company. All rights reserved.10 | 4 Question Methane (CH 4 ) is a gas, but carbon tetrachloride (CCl 4 ) is a liquid at room conditions. Which of the following statements explains this phenomenon? a)CCl 4 is a polar molecule and CH 4 is not. b)CCl 4 and CH 4 have different geometries and shapes. c)CH 4 exhibits hydrogen bonding and CCl 4 does not. d)Cl is more electronegative than H. e)None of these statements is correct.

Copyright © Houghton Mifflin Company. All rights reserved.10 | 5 Answer e)None of these statements is correct. Section 10.1, Intermolecular Forces Both molecules are nonpolar (both are tetrahedral). Because CCl 4 has more electrons than CH 4, its London forces are stronger, so CCl 4 is a liquid while CH 4 is a gas.

Copyright © Houghton Mifflin Company. All rights reserved.10 | 6 Question Which of the following species exhibits the strongest intermolecular forces? a)CH 4 b)H 2 O c)N 2 d)CO e)He

Copyright © Houghton Mifflin Company. All rights reserved.10 | 7 Answer b) H 2 O Section 10.1, Intermolecular Forces Water exhibits hydrogen bonding. Methane (CH 4 ), N 2, and He exhibit London dispersion forces. Carbon monoxide (CO) exhibits dipole–dipole interactions.

Copyright © Houghton Mifflin Company. All rights reserved.10 | 8 Question What type(s) of intermolecular forces is (are) exhibited by methane (CH 4 )? a)Hydrogen bonding and London dispersion forces b)Hydrogen bonding c)Dipole–dipole and London dispersion forces d)London dispersion forces

Copyright © Houghton Mifflin Company. All rights reserved.10 | 9 Answer d) London dispersion forces Section 10.1, Intermolecular Forces Methane is a nonpolar molecule (it has a tetrahedral geometry and shape), so it exhibits London dispersion forces.

Copyright © Houghton Mifflin Company. All rights reserved.10 | 10 Question When a water molecule forms a hydrogen bond with another water molecule, which atoms are involved in the interaction? a)A hydrogen atom from one water molecule, and a hydrogen atom from the other water molecule b)An oxygen atom from one water molecule, and an oxygen atom from the other water molecule c)A hydrogen atom from one water molecule, and an oxygen atom from the other water molecule d)Two hydrogen atoms from one water molecule, and one hydrogen atom from the other water molecule e)A hydrogen atom and an oxygen atom from the same water molecule

Copyright © Houghton Mifflin Company. All rights reserved.10 | 11 Answer c)A hydrogen atom from one water molecule, and an oxygen atom from the other water molecule. Section 10.1, Intermolecular Forces The hydrogen–oxygen chemical bond is quite polar, leaving the hydrogen with a partial positive charge and the oxygen with a partial negative charge. Thus the hydrogen from one water molecule has an attraction to the oxygen of the other water molecule.

Copyright © Houghton Mifflin Company. All rights reserved.10 | 12 Question Which of the following has the highest boiling point? a)H 2 O b)HF c)NH 3 d)N 2 e)Na 2 S

Copyright © Houghton Mifflin Company. All rights reserved.10 | 13 Answer e)Na 2 S Section 10.1, Intermolecular Forces The highest boiling point should result from an ionic compound with ion–ion forces of attraction. The only ionic compound in these choices is Na 2 S.

Copyright © Houghton Mifflin Company. All rights reserved.10 | 14 Question Which intermolecular force is the strongest? a)Dipole–dipole forces b)London dispersion forces c)Hydrogen bonding d)Ion–ion interactions

Copyright © Houghton Mifflin Company. All rights reserved.10 | 15 Answer d)Ion–ion interactions Section 10.1, Intermolecular Forces Intermolecular forces are strongest between the highest-charged species. These highest- charged species are ions with ionic forces.

Copyright © Houghton Mifflin Company. All rights reserved.10 | 16 Question Which of the following compounds has the lowest boiling point? a)C 2 H 6 b)C 3 H 8 c)CH 4 d)C 5 H 12 e)C 4 H 10

Copyright © Houghton Mifflin Company. All rights reserved.10 | 17 Answer c)CH 4 Section 10.1, Intermolecular Forces The lowest boiling point should result from the species with the weakest intermolecular forces. Of the species given here, CH 4 has the weakest London dispersion forces and is the smallest in size.

Copyright © Houghton Mifflin Company. All rights reserved.10 | 18 Question Which of the following is the correct order of boiling points for KNO 3, CH 3 OH, C 2 H 6, and Ne? a)KNO 3 < CH 3 OH < C 2 H 6 < Ne b)CH 3 OH < Ne < C 2 H 6 < KNO 3 c)Ne < C 2 H 6 < KNO 3 < CH 3 OH d)Ne < C 2 H 6 < CH 3 OH < KNO 3 e)C 2 H 6 < Ne < CH 3 OH < KNO 3

Copyright © Houghton Mifflin Company. All rights reserved.10 | 19 Answer d) Ne < C 2 H 6 < CH 3 OH < KNO 3 Section 10.1, Intermolecular Forces The boiling points are determined by size and intermolecular forces. Ne has the lowest boiling point because it is the smallest and has only London dispersion forces. C 2 H 6 is next; it has only London dispersion forces. CH 3 OH is next; it has dipole–dipole forces. KNO 3 has the highest boiling point, because it has ionic forces.

Copyright © Houghton Mifflin Company. All rights reserved.10 | 20 Question Consider two liquids, A and B. Liquid A exhibits stronger intermolecular forces than liquid B. Which of the following statements is true? a)The surface tension and viscosity of liquid A are greater than those of liquid B. b)The surface tension of liquid A is greater than that of liquid B; the viscosity of liquid B is greater than that of liquid A. c)The surface tension of liquid B is greater than that of liquid A; the viscosity of liquid A is greater than that of liquid B. d)The surface tension and viscosity of liquid B are greater than those of liquid A.

Copyright © Houghton Mifflin Company. All rights reserved.10 | 21 Answer a)The surface tension and viscosity of liquid A are greater than those of liquid B. Section 10.2, The Liquid State As the strength of intermolecular forces increases, both surface tension (a measure of a liquid’s resistance to an increase in its surface area) and viscosity (a measure of a liquid’s resistance to flow) generally increase.

Copyright © Houghton Mifflin Company. All rights reserved.10 | 22 Question A certain metal fluoride crystallizes in such a way that the fluoride ions occupy simple cubic lattice sites, while the metal atoms occupy the body centers of half the cubes. What is the formula for this metal fluoride? a)MF 2 b)M 2 F c)MF d)MF 6 e)MF 8

Copyright © Houghton Mifflin Company. All rights reserved.10 | 23 Answer a)MF 2 Section 10.4, Structure and Bonding in Metals; Section 10.7, Ionic Solids The fluoride ions occupy simple cubic lattice sites and the metal (M) ions occupy half of the body- centered sites, so the formula would be M ½ F or MF 2.

Copyright © Houghton Mifflin Company. All rights reserved.10 | 24 Question Which of the following statements is incorrect? a)Ionic solids generally have high melting points. b)Ionic solids are insulators. c)The binding forces in a molecular solid include London dispersion forces. d)Molecular solids generally have high melting points.

Copyright © Houghton Mifflin Company. All rights reserved.10 | 25 Answer d)Molecular solids generally have high melting points. Section 10.6, Molecular Solids; Section 10.7, Ionic Solids Molecular solids exhibit London dispersion forces, which indicate that they have low melting points. Ionic solids exhibit ionic forces, which indicate that they have high melting points and have the ability to be insulators. If the ionic compounds are molten, they are conductors.

Copyright © Houghton Mifflin Company. All rights reserved.10 | 26 Question A certain metal fluoride crystallizes in such a way that the fluoride ions occupy simple cubic lattice sites, while the metal ions occupy the body centers of half the cubes. Which of the following could be the metal ion? a)The calcium ion b)The sodium ion c)The iron(III) ion d)The vanadium(IV) ion e)Any of the above ions

Copyright © Houghton Mifflin Company. All rights reserved.10 | 27 Answer a)The calcium ion Section 10.6, Molecular Solids; Section 10.7, Ionic Solids Each unit cell contains one F - ion. Because the metal ions are in half the unit cells, the metal ion must have a +2 charge. The only choice with a +2 charge is the calcium ion.

Copyright © Houghton Mifflin Company. All rights reserved.10 | 28 Question Consider the following boiling point data and decide which liquid has the highest vapor pressure at room temperature: a)Water, H 2 O100°C b)Methanol, CH 3 OH64.96°C c)Ethanol, CH 3 CH 2 OH78.5°C d)Diethyl ether, CH 3 CH 2 –O–CH 2 CH °C e)Ethylene glycol, HO–CH 2 –CH 2 –OH198°C

Copyright © Houghton Mifflin Company. All rights reserved.10 | 29 Answer d)Diethyl ether, CH 3 CH 2 –O–CH 2 CH 3 Section 10.8, Vapor Pressure and Changes of State The substance with the lowest boiling point should have the highest vapor pressure at room temperature.

Copyright © Houghton Mifflin Company. All rights reserved.10 | 30 Question Given the graph below, what is the boiling point of carbon tetrachloride at standard pressure? a)60°C b)34°C c)98°C d)77°C

Copyright © Houghton Mifflin Company. All rights reserved.10 | 31 Answer c)77°C Section 10.8, Vapor Pressure and Changes of State According to the graph, at 760 torr vapor pressure the temperature of CCl 4 is 77°C, which is its boiling point.

Copyright © Houghton Mifflin Company. All rights reserved.10 | 32 Question Which of the following would you expect to have the lowest vapor pressure? a)CH 3 OCH 3 b)CH 3 CH 2 OH c)CH 3 CH 2 CH 3 d)CH 3 CH 2 CH 2 CH 3 e)H 2 O

Copyright © Houghton Mifflin Company. All rights reserved.10 | 33 Answer e) H 2 O Section 10.8, Vapor Pressure and Changes of State Water exhibits hydrogen bonding, as does ethanol (choice b). However, there are two hydrogen atoms on water that can hydrogen-bond to other water molecules. Because the intermolecular forces exhibited by water are greater than the intermolecular forces for the other choices, its vapor pressure would be the lowest.

Copyright © Houghton Mifflin Company. All rights reserved.10 | 34 Question What is the vapor pressure of water at 70  C? a)5.00 atm b)1.20 atm c)1.00 atm d)0.31 atm

Copyright © Houghton Mifflin Company. All rights reserved.10 | 35 Answer d) 0.31 atm Section 10.8, Vapor Pressure and Changes of State The normal boiling point of water (i.e., the temperature at which water boils at 1 atm) is 100°C, so the vapor pressure of water at 100°C is 1 atm. Because vapor pressure increases with increasing temperature, the vapor pressure at 70°C must be less than 1 atm. Only one choice (0.31 atm) is less than 1 atm.