CHAPTER 10 2009-Zumdahl - Chapter 10 - LIQUIDS and SOLIDS...

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Unformatted text preview: Chapter 10 - LIQUIDS and SOLIDS 10.1 Intermolecular Forces a. Intermolecular forces are attractive forces between molecules (or particles) that make up a substance and they are especially important in liquids and solids. b. Attractive intermolecular forces enable real gases to condense and form liquids. Because molecules or particles in gases are generally very far apart from one another, the influence of intermolecular forces is negligible and is normally ignored. c. However, because of the close proximity of molecules to each other in the liquids and solids, intermolecular forces play important roles in determining the physical properties of liquids and solids. d. Intermolecular forces are responsible for many properties of liquids, such as surface tension, viscosity, capillary action, vapor pressure, boiling point, and enthalpy of vaporization. e. Types of Intermolecular Forces in Liquids: i- London Dispersion Forces (LDFs): instantaneous dipole ii- Dipole-Dipole interactions iii- Hydrogen Bonds i- London Dispersion Forces (LDFs): instantaneous dipole (Figure 10.5) Van der Waals A. An instantaneous dipole which arises from momentary imbalances in e- distribution within the molecule B. Present in all covalent molecules a. As the # of e- s (mass/size) increases, the strength of the LDF increases C. Weakest IMF D. The predominate IMF in nonpolar molecules such as: a. Monatomic gases: He, Ne, Ar, Kr, Xe, Rn b. Molecules with polar bonds, yet because of molecular symmetry, the overall molecule is non polar: CH 4 c. Diatomic molecules: H 2 , O 2 , F 2 , Br 2 , I 2 , N 2 , Cl 2 d. Hydrocarbons: alkanes, alkenes, alkynes 1 Weakest Strongest e. The momentary instantaneous polarization is most pronounced when the molecule is moving slowly (low temp) ii- Dipole-Dipole Interactions: (Figure 10.2) A. Created between 2 polar molecules because of the partial + and charges on the dipole caused by significant differences in e- neg of the atoms in the bond B. About 1% as strong as a covalent bond Intermediate in strength C. Present in all polar molecules iii- Hydrogen Bonding: (Figure 10.4) A. A special type of dipole-dipole where hydrogen is bonded to small, highly electronegative elements of FON B. 2 factors account for the strength of the force a. The great polarity in the H-O, H-F, H-N bonds b. The close approach of the dipoles allowed for by the small size of the hydrogen atom and the 3 atoms of FON C. The strongest of the IMFs and accounts for the unusually high MP and BP of group 15, 16, 17 hydrides of period 2 (as compared to period 3, 4, 5, etc) iv- Molecule-Ion Attraction: (Figure 7.2) 2 A.A....
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This note was uploaded on 06/20/2011 for the course CHEM 111A taught by Professor Hockings during the Fall '08 term at Washington University in St. Louis.

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CHAPTER 10 2009-Zumdahl - Chapter 10 - LIQUIDS and SOLIDS...

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