Chapter 12 Intermolecular Forces

Chapter 12 Intermolecular Forces - Chapter 12...

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12 Chapter Intermolecular Forces: Liquids, Solids, and Phase Changes 12.1 In a solid, the energy of attraction is greater than the energy of motion, while in a gas, it is less. Gases have high compressibility and the ability to flow, while solids have neither of these properties. 12.2 a)-c) intermolecular d) intramolecular 12.3 a) Because the distance between particles is much greater in the gas. b) Because the interparticle forces are greater in the solid. 12.4 a) Because the intermolecular forces are only partially overcome in fusion and need to be totally overcome in vaporization. b) Because greater intermolecular forces are found in solids as opposed to liquids. c) H COND = -∆ H VAP . 12.5 a), b) intermolecular; c), d) intramolecular 12.6 a), c), d) intermolecular; b) intramolecular 12.7 a) condensation b) melting (fusion) c) evaporation 12.8 a) deposition b) sublimation c) crystallization (freezing) 12.9 The molecules of a gas are moving more rapidly than those in a liquid. When the liquid condenses, the molecules slow down and energy is released to the surroundings. 12.10 Sublimation and deposition. 12.11 The gaseous PCl 3 molecules are moving faster than and are farther apart than the liquid molecules. As they condense, the kinetic energy of the molecules is changed into potential energy stored in the dipole-dipole interactions between the molecules. 12.12 The two processes are the formation of solid from liquid and the formation of liquid from solid (at the macroscopic level). At the molecular level, the two processes are the removal of kinetic energy from the liquid molecules as they solidify and the overcoming of the dispersion forces between the molecules as they turn to liquid. 12.13 At first, the evaporation of liquid molecules from the surface predominates, which increases the number of gas molecules and hence the vapor pressure. Once more molecules enter the gas phase, the probability of a gas molecule hitting the surface of the liquid and "sticking" increases, so the condensation rate increases. When the evaporation and condensation rates become equal, the vapor pressure becomes constant. 12.14 As intermolecular forces increase, the a) critical temperature increases. b) boiling point increases. c) vapor pressure decreases. d) heat of vaporization increases. 205
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12.15 No. At 1.1 atm, water boils at a temperature above 100 o C, since it is more difficult for gas molecules to escape the liquid when the applied pressure is greater. 12.16 a) The final pressure will be the same, since the vapor pressure is constant as long as some liquid is present. b) The final pressure will be lower, according to Boyle's Law. 12.17 If the solid is more dense than the liquid, the solid-liquid line slopes to the right; if less dense, to the left. 12.18
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Chapter 12 Intermolecular Forces - Chapter 12...

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