Chemistry 111 week of 1/25/16
Chemistry 111 week of 1/25/16 111001
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This 4 page Class Notes was uploaded by Audrey Notetaker on Saturday January 30, 2016. The Class Notes belongs to 111001 at Boston College taught by Neil Wolfman in Fall 2016. Since its upload, it has received 24 views. For similar materials see General Chemistry II in Chemistry at Boston College.
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Date Created: 01/30/16
Chapter 11: Vapor Pressure of Liquids 1/25/16 Capillary Action: the ability of liquid to flow up a narrow tube against gravity Adhesive – molecules stick to the wall Cohesive – molecules stick to each other if the adhesive force is greater than the cohesive, then the liquid will creep up the side (i.e. water) if the cohesive force is greater than the adhesive, then the liquid will bulge (i.e. mercury) Dynamic Equilibrium: rate of evaporation = rate of condensation the rate of evaporation is a constant and only dependent on temperature vapor pressure is a constant and only dependent on temperature *liquids with a high vapor pressure are volatile Normal Boiling Point: the temperature at which pressure is at 1 atm. A liquid has reached its boiling point when the vapor pressure of liquid = the ambient pressure (1 atm). Freezing point and melting point does not depend on pressure because solids and liquids cannot be compressed *temperature does not change during a phase change ∆ Hvap = how much heat it takes to heat a substance over a certain amount of time. Always positive and larger than H fus ln P2 =−∆ H ( 1 − 1 ) (P1 R T2 T 1 R= 8.314 J/mol*K Chapter 11: Phase Diagrams 1/27/16 ln P2 =−∆ H ( 1 − 1 ) (P1 R T2 T 1 R= 8.314 J/mol*K *pressure, delta H, and temperature should never be negative *vapor pressure goes up if the temperature goes up Phase Diagram: the lines represent equilibrium if the line representing the change from solid to liquid leans to the right, the solid is more dense than the liquid if the line representing the change from liquid to solid leans to the left, the liquid is more dense than the solid (i.e. water) all three phases are at equilibrium at the triple point there is no liquid below the triple point Supercritical Fluid: there is no differentiation between liquid and gas. Takes place above the critical point. Critical Point: point at which a substance can no longer exist as a liquid Critical Pressure: minimal pressure needed to liquefy a gas at critical temperature There are different forms of ice at high pressures *water moderates temperature *water is a universal solvent because of its polarity Solids: essentially incompressible Intermolecular forces within solids molecular nonbinding atomic metallic atomic ionic covalent Molecular: weak intermolecular forces – low melting points H2O, CO2 Nonbinding atomic: weak London forces – low melting points Noble gases Metallic atomic: Transition metals Chapter 11: Unit Cells and Cubic Systems 1/29/16 Ionic Solids: cations and anions NaBr, KOH, MgF2 Covalent Solids: atoms, molecules held together in networks or chains Graphite, diamond, quartz *highest melting point *Stronger forces = higher melting point melting point instead of boiling because it’s a solid Hardness: how easily structural units can be moved Molecular solids – soft ionic solids – hard, brittle 3D covalent networks – hardest substance metallic solid not brittle, malleable, conducts electricity Amorphous: no longrange order (i.e. glass, plastic) Crystalline: ordered (NaCl, sucrose) Crystal: 3D ordered arrangement “unit cell” – brick/building block when replicated in all three dimensions can give entire lattice structure *different unit cell shape is based on edge length and angle Types of crystals: Cubic System Simple cubic (1/8 *8) = 1 atom per unit cell o 8 other unit cells share the same corner/make up the atom Coordination number = 6 Packing efficiency = 52% Edge length (l) = 2*r(radius) Bodycentered cubic (1/8 *8) + 1 = 2 atoms per unit cell Coordination number = 8 Packing efficiency = 68% Edge length (l) = 4*r Facecentered cubic (1/8 *8) + (1/2 *6) = 4 atoms per unit cell Coordination number = 12 Packing efficiency = 74% Edge length (l) = 4*r (diagonal across the face)
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