Chapter 13 Phase Diagrams
Chapter 13 Phase Diagrams CHEM 1200
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This 4 page Class Notes was uploaded by Alexi Martin on Monday February 22, 2016. The Class Notes belongs to CHEM 1200 at Rensselaer Polytechnic Institute taught by Dr. Alexander Ma in Spring 2016. Since its upload, it has received 15 views. For similar materials see Chemistry II in Chemistry at Rensselaer Polytechnic Institute.
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Date Created: 02/22/16
Ch 13 Phase Diagrams and Crystalline Solids Phase Diaqrams different states and state changes occur at a certain temperature and pressure regions represent different states ine equilibrium i iquid to gas vapor pressure curve boiling curvevaporization curve both states exist at equilibrium jv s s s s e e e s s s e e e s s s e e s scannm n s s s e e s s s s s s s es critica point X furthest point on vapor E Fillid pressure curve 3 point T is all phases at equilibrium 1 a omt Increases as pressure mg 7 r WEE Water reclid Zr iquid at room temperature Hydrogen bonding excelent solvent ionic and polar dissolve and nonpolar high specific heat expand when it freezes Crystal Lattice cools slowly particles in liquid will arrange themselves with max attractive forces decreases energy Unit Cells 3D repeat unit over and over each particlelattice point number of particles in contact equals the coordination ions oppositely charged increase in coordination more interactions stronger attractive forces packing efficiency in volume in unit cell occupied by particles IUD temptin r Willi1 90 degree angles length corner within an edge Vedge length cubed sphere 431Trquot2 Simple Cubic Radius8 8 particles at each corner 8x18 1 particle in each unit cell edge2r coordination 6 packing efficiency V particles V of unit cell x100 gt 52 Unit Cells Bodv Centered Cubic 9 particles corner 8x18 1 center 2 particles inside edge43quot12x r particle coordination 8 68 packing efficiency Face Centered Cubic 14 particles 4 particles inside 74 packing efficiency edge 22rquot12 Coordination 12 example 1 22quot12 x 143 x10quot8 density of Al FCC r143 pm10quot12 m Dgcmquot3 4045x10A8 4269826022x10quot23 1 792x10quot22 g6618x10quot23m V6618x10quot23 d 271 gcmquot3 143 x10quot1210quot2 example 2 2475 pm x10quot1210quot2 43M22475x 10quot8 285476022x10quot23m m2839x10quot22 g1868x10quot22 57x10quot8quot3 V1868x10quot22 Rb r2475 pm d1520 gcmquot3 Closest Packed Structures1st layer spheres more efficient to offset each row in the gaps of the previous row than to line up rows and columns third layer Hexagonal closest packed Second layer simple cubic can sit directly over the atoms in the first called an AA pattern second layer can sit over the holes in the first layer AB pattern Third Layer with offset 2nd layer directly over the atoms in the 1st layer ABA pattern body centered cubic third layer can sit over uncovered holes in the first layer ABC pattern face centered cubic Xrav crvstallooraphv x rays passed through a crystalline solidabsorbed most remitted out of phase or in phase and recorded on a film lnterpreting Diffraction data 2D hit lattice are deflection Bragg equation n is an integer lambda is the wavelength d is the interplane spacing and theda you are solving for Aquoto10quot10 m example 3 n1 G505 A1315Aquoto n A2 dsinG 113152SIN505 d283 Aquoto example 4 2x2quot12 362 r128 Aquoto128 pm Classifvinci Crvstalline Solids kinds of particles found can be subclassified molecular solids molecules such as water weak interactions ionic solids ions strong interactions table salt atomic solids atoms a ion bonding dispersion forces such as Ne atoms b metallic bonding metallic bonds between metals in alloys or other metals JONA39 c network covalent bonding covalent bonds between other atoms such as graphite or diamond Molecular Solid exampes include C02 H20 C12H22011 dispersion dipoledipole and H bonding gt300 degrees Celsius melting pointing Ionic Solid opposite charged ions non directional coordination counter cation and anion interactions greater the coordination the more stable the solid allow it depends on the size of the charge 0 note from here on you may want to look at outside sources and models to understand these concepts they are mainly conceptual and are hard to understand Lattice Holes octahedra hole is an octahedral tetrahedral holes are smaller hexagona cp or FCC lattice 3 octahedral and 4 tetrahedral simpe cubic 1 cubic hole number and type of holes determines empirical formula of the salt example 5 GaAs cations Ga sits in a 12 octahedral hoe4 Ar 8x126x124 GaAs Nonbonding atomic solids solid noble gases weak dispersion forces low melting point arrange hexagonal cp or face centered cubic max attractive forces decreases energy Metallic atomic solids strength varies with size and charge according to coulombic attraction meting point varies cosest packed arrangements cations metas have slip planes can slide more slip panesmore ductile Network covalent solids attached by covalent bonds do not form closely packed crystals melting point is above 1000 degrees celsius dimensionality affects physical properties 1Diamond 3D spquot3 tetrahedral one molecule with covalent bonds melting point 3800 degrees celsius rigid and hard covalent bonds and directionality electrical insulator thermal conductor non reactive 2Graphite 2D spquot2 benzene rings trigonal planar giant molecule 341 pm apart stacked hexagonal greater melting point than 3800 degrees celsius insulator thermal nonreactive slippery lubricant electrical conductor 3 Silicates 90 of earth s crust glas amorphous SiO molecules A Quartz Si02 impurities add color tetrahedral about 1600 degrees celsius melting point very hard types of gemstones example 6 greater the melting point gt listed from lowest to highest KCI Cs K SIOZ
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