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Unformatted text preview: 11 Intermolecular Forces, Liquids and Solids Visualizing Concepts 11.2 (a) Hydrogen bonding; HF interactions qualify for this narrowly defined interaction. (b) London dispersion forces, the only intermolecular forces between nonpolar F 2 molecules. (c) Ion-dipole forces between Na + cation and the negative end of a polar covalent water molecule. (d) Dipole-dipole forces between oppositely charged portions of two polar covalent SO 2 molecules. 11.3 The viscosity of glycerol will be greater than that of 1-propanol. Viscosity is the resistance of a substance to flow. The stronger the intermolecular forces in a liquid, the greater its viscosity. Hydrogen bonding is the predominant force for both molecules. Glycerol has three times as many OH groups and many more H-bonding interactions than 1-propanol, so it experiences stronger intermolecular forces and greater viscosity. (Both molecules have the same carbon- chain length, so dispersion forces are similar.) 11.5 The stronger the intermolecular forces, the greater the average kinetic energy required to escape these forces, and the higher the boiling point. CH 3 CH 2 CH 2 OH has hydrogen bonding, by virtue of its OH group, so it has the higher boiling point. Dispersion forces are similar because molar masses are the same for both molecules. 11.6 (a) 360 K, the normal boiling point; 265 K, normal freezing point. The left-most line is the freezing/melting curve, the right-most line is the condensation/boiling curve. The normal boiling and freezing points are the temperatures of boiling and freezing at 1 atm pressure. (b) The material is solid in the white zone, liquid in the blue zone, and gas in the yellow zone. (i) gas (ii) solid (iii) liquid 11.8 (a) Clearly, the structure is close-packed. The question is: cubic or hexagonal? Without looking deeper into the layers of oranges, one cannot distinguish whether the layer structure is cubic (ABCABC) or hexagonal (ABABAB) close-packed. (b) CN = 12, regardless of whether the structure is hexagonal or cubic close packed. (c) Molecular. There are no strong bonds between particles. Kinetic-Molecular Theory 11.10 (a) In solids, particles are in essentially fixed positions relative to each other, so the average 160 11 Intermolecular Forces Solutions to Black Exercises energy of attraction is stronger than average kinetic energy. In liquids, particles are close together but moving relative to each other. The average attractive energy and average kinetic energy are approximately balanced. In gases, particles are far apart and in constant, random motion. Average kinetic energy is much greater than average energy of constant, random motion....
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