Intermolecular Forces: Liquids, Solids and Hydrogen Bonding, Study notes of Chemistry

Download Intermolecular Forces: Liquids, Solids and Hydrogen Bonding and more Study notes Chemistry in PDF only on Docsity! Chapter 10: Liquids, Solids and Intermolecular Forces Suggested end-of-chapter problems (the answers are given in the Appendix): Review: 22, 32, 34, 36, 40, 42 New: 26, 46, 48, 50, 56, 68, 84, 86, 88 Review: Interspecies forces are responsible for physical properties of materials -The stronger the attraction, the higher the boiling point, melting point, viscosity, and the lower the vapor pressure. A. Ionic bonds (200-1000 kJ/mol): attraction increases with increasing charge and decreasing ion size. B. Intermolecular forces (a.k.a. van der Waals forces): 1. Hydrogen bonding (10-40 kJ/mol): affects molecules with H-N, H-O, and/or H-F bonds only 2. Dipole-dipole (3-4 kJ/mol): affects polar molecules only. Increases as dipole moment increases. 3. London Dispersion (1-10 kJ/mol) -"induced dipole": increases with no. of electrons and length. 4. Ion-Dipole: (10-50 kJ/mol)- occurs between ions and polar solvents C. Some Properties of Liquids: A. Viscosity: liquid’s resistance to flow B. Surface Tension: liquid’s tendency to minimize its surface area I. Evaporation, Vapor Pressure and Boiling Point II. Phase Changes: A. Enthalpy changes: 1. +H for sublimation, vaporization and fusion (melting) -H for deposition, condensation and freezing 2. Hvap > Hfusion B. Heating Curves C. Phase Diagrams: Triple Point, Critical Point (Critical Temperature, Critical Pressure), "Normal" Boiling Point and "Normal" Melting Point occur at 1 atm of pressure III. Solid Structures (amorphous vs. crystalline solids) A. Units cells are classified by their symmetry, e.g. simple cubic, body- centered cubic, face-centered cubic. B. Fundamental types: 1. Molecular solids-units are molecules held together by intermolecular attractions (H-bonding, dipole-dipole, and dispersion forces). Also included are the noble gases. Examples: H2O, CO2, S8, Ne, Ar, He, Xe, He, Kr, Rn 2. Ionic solids –units are cations and anions, held together by electrostatic attractions. Examples: NaCl, ZnS, CaF2 3. Metallic Crystals-units are metal cations in a sea of valence electrons (electrostatic attractions). Examples: Cr, Fe, Cu, Ca, Na 4. Network covalent crystals-units are nonmetals or semimetals, held together by covalent bonds. Ex: C (diamond or graphite), Si, Ge, Sn, P, As, Se, Te, SiC, SiO2.