Chapter 12: Liquids, Solids and Intermolecular Forces Chemistry 140 Fall 2002 General Chemistry Principles and Modern Applications Petrucci • Harwood • Herring 8th Edition Chapter 12: Liquids, Solids and Intermolecular Forces Philip Dutton University of Windsor, Canada N9B 3P4 Prentice-Hall © 2002

General Chemistry: Chapter 13 Chemistry 140 Fall 2002 Contents 12-1 Intermolecular Forces and some Properties of Liquids 12-2 Vaporization of Liquids: Vapor Pressure 12-3 Some Properties of Solids 12-4 Phase Diagrams 12-5 Van der Waals Forces 12-6 Hydrogen Bonding 12-7 Chemical Bonds as Intermolecular Forces 12-8 Crystal structures 12-8 Energy Changes in the Formation of Ionic Crystals Focus on Liquid Crystals Prentice-Hall © 2002 General Chemistry: Chapter 13

12-1 Intermolecular Forces and Some Properties of Liquids Cohesive Forces Intermolecular forces between like molecules. Adhesive Forces Intermolecular forces between unlike molecules. Surface Tension Energy or work required to increase the surface area of a liquid. Viscosity A liquids resistance to flow Prentice-Hall © 2002 General Chemistry: Chapter 13

Intermolecular Forces Prentice-Hall © 2002 General Chemistry: Chapter 13

Intermolecular Forces Prentice-Hall © 2002 General Chemistry: Chapter 13

12-2 Vaporization of Liquids: Vapor Pressure Chemistry 140 Fall 2002 12-2 Vaporization of Liquids: Vapor Pressure Bonding atomic orbitals are shown in grey. Prentice-Hall © 2002 General Chemistry: Chapter 13

Enthalpy of Vaporization ΔHvap = Hvapor – Hliquid = - ΔHcondensation Prentice-Hall © 2002 General Chemistry: Chapter 13

Boiling Point Mercury manometer Vapor pressure of liquid Pvap independent of Vliq Pvap independent of Vgas Pvap dependent on T Prentice-Hall © 2002 General Chemistry: Chapter 13

Vapor Pressure and Boiling Point (e) (d) (c) (b) (a) Ln P = -A ( ) + B 1 T A = ΔHvap R Prentice-Hall © 2002 General Chemistry: Chapter 13

Clausius-Clapeyron Equation Ln P = -A ( ) + B 1 T Ln = - ( - ) P2 P1 1 T2 T1 ΔHvap R Example 12-1: The vapor pressure is  5.08 kPa at 18.1 °C, the vaporization enthalpy is  41.9 kJ/mol. What is the vapor pressure at 61.1 °C? Example 12-2: A compound has a 5.258 kPa vapor pressure at 15.80 °C. At 40.35 °C it has 45.61 kPa vapor pressure.  What is the molar enthalpy of vaporization in J mol-1 of this compound? Prentice-Hall © 2002 General Chemistry: Chapter 13

12-3 Some Properties of Solids Freezing Point Melting Point ΔHfus(H2O) = +6.01 kJ/mol Prentice-Hall © 2002 General Chemistry: Chapter 13

General Chemistry: Chapter 13 Sublimation ΔHsub = ΔHfus + ΔHvap = -ΔHdeposition Prentice-Hall © 2002 General Chemistry: Chapter 13

General Chemistry: Chapter 13 Chemistry 140 Fall 2002 12-4 Phase Diagrams Iodine OD represents the FUSION CURVE. There is little effect of pressure on melting point. O is the triple point. A unique temperature and pressure at which three states of matter coexist in equilibrium. Prentice-Hall © 2002 General Chemistry: Chapter 13

General Chemistry: Chapter 13 Chemistry 140 Fall 2002 Phase Diagrams Carbon dioxide Triple point is greater than one atmosphere, so we do not form liquid. Sublimation occurs. Liquid present in fire extinguishers (P > 5.1 atm) Prentice-Hall © 2002 General Chemistry: Chapter 13

General Chemistry: Chapter 13 Supercritical Fluids Prentice-Hall © 2002 General Chemistry: Chapter 13

General Chemistry: Chapter 13 Chemistry 140 Fall 2002 Phase Diagram of Water Fusion curve (OD) has a negative slope. Unusual behavior. Ice skating. Polymorphysm, the existence of a solid substance in more than one form. This is common. Prentice-Hall © 2002 General Chemistry: Chapter 13

General Chemistry: Chapter 13 The Critical Point Prentice-Hall © 2002 General Chemistry: Chapter 13

Critical Temperatures and Pressures Prentice-Hall © 2002 General Chemistry: Chapter 13

3 dimension p-V-T surface Csonka Gábor © 2008 Általános kémia: 3. fejezet

Water 3 dimension p-V-T surface

Van der Waals Constants The Van der Waals constants can be obtained from the critical data: a = 3pc Vc3 and b = Vc/3 Csonka Gábor © 2008 Általános kémia: 3. fejezet

General Chemistry: Chapter 13 12-5 Van der Waals Forces Instantaneous dipoles. Electrons move in an orbital to cause a polarization. Induced dipoles. Electrons move in response to an outside force. Dispersion or London forces. Instaneous dipole – induced dipole attraction. Related to polarizability. Prentice-Hall © 2002 General Chemistry: Chapter 13

Phenomenon of Induction Prentice-Hall © 2002 General Chemistry: Chapter 13

Instantaneous and Induced Dipoles Prentice-Hall © 2002 General Chemistry: Chapter 13

London dispersion in hydrocarbons C5H12 C15H32 C18H38

Dipole Dipole Interactions Prentice-Hall © 2002 General Chemistry: Chapter 13

The water molecule (dipole moment) Dipole moment:  = 1.85 Debye Polarizability: α = 1.48 x 10-24 cm3 δ- δ+ General Chemistry: Chapter 13

General Chemistry: Chapter 13 12-6 Hydrogen Bonding Prentice-Hall © 2002 General Chemistry: Chapter 13

Hydrogen Bonding in HF(g) Prentice-Hall © 2002 General Chemistry: Chapter 13

Hydrogen Bonding in Water Chemistry 140 Fall 2002 Hydrogen Bonding in Water Solid ice has lower density than liquid water. H-bonding holds the ice in a rigid but open structure. Maximum density of water at 3.98 C. around a molecule in the solid in the liquid Prentice-Hall © 2002 General Chemistry: Chapter 13

Other examples of H-Bonds Chemistry 140 Fall 2002 Other examples of H-Bonds Viscosity Units centipoise (cP). Water at 20 C 1 cP. Prentice-Hall © 2002 General Chemistry: Chapter 13

12-7 Chemical Bonds as Intermolecular Forces Chemistry 140 Fall 2002 12-7 Chemical Bonds as Intermolecular Forces Network covalent solids. C allotropes: Diamond and Graphite Prentice-Hall © 2002 General Chemistry: Chapter 13

Other Carbon Allotropes Prentice-Hall © 2002 General Chemistry: Chapter 13

General Chemistry: Chapter 13 Interionic Forces Prentice-Hall © 2002 General Chemistry: Chapter 13

General Chemistry: Chapter 13 12-8 Crystal Structures Prentice-Hall © 2002 General Chemistry: Chapter 13

Unit Cells in the Cubic Crystal System Prentice-Hall © 2002 General Chemistry: Chapter 13

General Chemistry: Chapter 13 Holes in Crystals Prentice-Hall © 2002 General Chemistry: Chapter 13

Hexagonal Close Packed (hcp) Prentice-Hall © 2002 General Chemistry: Chapter 13

General Chemistry: Chapter 13 Coordination Number Prentice-Hall © 2002 General Chemistry: Chapter 13

Counting Cell Occupancy Prentice-Hall © 2002 General Chemistry: Chapter 13

General Chemistry: Chapter 13 X-Ray Diffraction Prentice-Hall © 2002 General Chemistry: Chapter 13

General Chemistry: Chapter 13 X-Ray Diffraction Prentice-Hall © 2002 General Chemistry: Chapter 13

General Chemistry: Chapter 13 Cesium Chloride Prentice-Hall © 2002 General Chemistry: Chapter 13

Atomic Radii from Crystal Structures Chemistry 140 Fall 2002 Atomic Radii from Crystal Structures Prentice-Hall © 2002 General Chemistry: Chapter 13

General Chemistry: Chapter 13 Sodium Chloride Prentice-Hall © 2002 General Chemistry: Chapter 13

General Chemistry: Chapter 13 Holes in Crystals Prentice-Hall © 2002 General Chemistry: Chapter 13

General Chemistry: Chapter 13 Prentice-Hall © 2002 General Chemistry: Chapter 13

12-9 Energy Changes in the Formation of Ionic Crystals Prentice-Hall © 2002 General Chemistry: Chapter 13

General Chemistry: Chapter 13 Chapter 13 Questions 1, 3, 4, 13, 24, 26, 31, 45, 52, 61, 94, 107 Prentice-Hall © 2002 General Chemistry: Chapter 13