Chem 1212: Chapters 12-14 – Flashcards
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Boyle's Law |
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P1V1=P2V2 |
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Charles' Law |
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V1/T1=V2/T2 |
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Combined Gas Law |
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P1V1/T1=P2V2/T2 |
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Avogadro's Law |
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At the same temperature and pressure, equal volumes of all gases contain the same number of molecules. |
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Standard Molar Volume |
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22.4 L -- One mole of an ideal gas occupies 22.4 L at 0C and 1 atm of pressure. |
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Ideal Gas Equation |
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PV=nRT |
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Dalton's Law of Partial Pressures |
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The total pressure exerted by a mixture of ideal gases is the sum of the partial pressures of those gases. |
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Vapor Pressure |
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Pressure exerted by its gaseous molecules in equilibrium with the liquid. |
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Kinetic-Molecular Theory |
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1. Gases consist of discrete molecules. The individual molecules are very small and far apart relative to their sizes. 2. Gaseous molecules are in continuous, rapid random, straight-line motion with varying velocities. 3. The collisions between gas molecules and with the walls of the container are elastic; the total energy is conserved during a collision. 4. Between collisions, the molecules exert no attractive or repulsive forces on one another; each molecule travels in a straight line with a constant velocity. |
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Root Mean Square |
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Urms=sq rt(3RT/Mm) R=8.314 kg m2/s2 K mol Molar mass, Mm, must be in KG/mol |
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Effusion |
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Gases exiting through the walls of a container with porous walls. |
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Diffusion |
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The movement of a substance into a space or the mixing of one substance with another. |
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Ratio of Rate of Effusion |
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R1/R2=sqrt(M2/M1) OR (D2/D1) |
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Deviations from Ideality |
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When molecules become close together through increased T or P -- intermolecular forces become important. |
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Miscible Liquids |
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Diffuse into each other; they are soluble in each other and form homogeneous solutions. |
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Intermolecular Forces |
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Forces between (among) individual particles (atoms, ions, molecules). |
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Ion-Ion Interactions |
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Force of attraction between two oppositely charged ions is governed by Coulomb's Law: F=abs(q1q2)/r2 F=magnitude of force r=distance in m q1,q2=charges on bodies (coulombs) |
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Intermolecular Interaction Strengths |
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I-I>HB>D-D>>LF |
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Dipole-Dipole |
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Occur between the + end of one polar molecule and the - end of the other. |
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Hydrogen Bonding |
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Especially strong D-D interaction. Occurs between an H atom in one molecule (attached to an F, O, or N), and an F, O, or N atom in another molecule. |
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Dispersion Forces (London Forces) |
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Present in all substances. ONLY kind of interactions for nonpolar substances. Result from the attraction of the nucleus of one atom for the electron cloud of another atom (in a different molecule). They increase with increasing polarizability, the ability of an electron cloud to be distorted. Polarizability increases with increasing numbers of electrons and therefore with increasing sizes of molecules. |
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Ion-Dipole Interactions |
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Ion and Dipole. Weaker than Dipole-Dipole. |
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Change in EN |
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Nonpolar: 0-0.5 Polar: 0.5-2.0 Ionic: > 2.0 |
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Viscosity |
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Resistance to flow. One measure of the forces of attraction within a liquid. Honey = high viscosity; gasoline = low viscosity. |
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Surface Tension |
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Measure of the inward forces that must be overcome to expand the surface of a liquid. Molecules on the surface are attracted only toward the interior, while those on the interior are attracted equally in all directions. |
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Capillary Action |
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Capillary Rise: Adhesive Forces > Cohesive Forces Capillary Fall: Cohesive Forces > Adhesive Forces |
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Evaporation |
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Process by which molecules escape from the surface of a liquid (vaporize). Occurs more rapidly as temperature increases because a greater fraction of molecules possess the necessary escape velocity and kinetic energy. |
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LeChatelier's Principle |
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A system at equilibrium, or changing toward equilibrium, responds in the way that tends to relieve or "undo" any stress placed on it. |
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Vapor Pressure |
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Pressure exerted by the vapor of the liquid on its surface at equilibrium in a closed container. Because vapor pressures increase as temperature increases, evaporation occurs more rapidly as T increases. |
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Boiling Point |
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Temperature at which the vapor pressure of the liquid equals the applied (usually atmospheric) pressure. |
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Distillation |
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Process by which a mixture or solution is separated into its components on the basis of differences in BPs of the components. |
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Specific Heat |
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Amount of heat required to raise the T of 1g of a substance 1C with no change in state. Q=mC(change in T) |
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Molar Heat Capacity |
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Amount of heat required to raise the temperature of 1 mol of a substance 1C with no change in state. Q=mol x molar heat capacity x change in T |
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Heat of Vaporization |
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Amount of heat that must be absorbed to convert 1g of a liquid at its BP to a gas with no change in temperature. Usually J/g. |
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Heat of Condensation |
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Reverse of Heat of Vaporization. Amount of heat that must be released to liquefy 1g of a gas at its condensation (BP) with no change in T. |
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Molar Heat of Vaporization |
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The amount of heat that must be absorbed to convert one mole of a liquid at its BP to a gas with no change in T. |
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Molar Heat of Condensation |
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Reverse of molar heat of vaporization. |
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Melting Point |
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Temperature at which liquid and solid coexist at equilibrium under a pressure of 1 atm. |
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Heat of Fusion |
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The amount of heat required to melt 1g of a solid at its melting point with no change in T. Endothermic. |
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Heat of Crystallization |
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Amount of heat liberated by the crystallization of one gram of liquid at its freezing point. Exothermic. |
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Specific Heat of Water |
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4.18 J/gC |
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Density of Water |
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1.00 g/mL |
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Specific Heat of Ice |
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2.09 J/gC |
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Sublimation |
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Conversion of a solid directly into vapor. Dry Ice is solid CO2. The white vapors are due to water condensing in the very cold gaseous CO2 near the solid. |
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Deposition |
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Vapor directly to solid. |
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Triple Point |
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Point at which three phases of a substance can coexist in equilibrium. |
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Critical Temperature |
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Temperature above which a gas cannot be liquefied, i.e., the temperature above which the liquid and gas do not exist as distinct phases. |
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Amorphous Solids |
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Have no well-defined ordered structure. Waxes, asphalt, and glass. |
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Critical Pressure |
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Pressure required to liquefy a gas at its critical temperature. |
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Critical Point |
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The combination of critical temperature and critical pressure. |
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Metallic Solids |
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Metals. |
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Ionic Solids |
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Consist of positive and negative ions arranged in a definite crystal structure. Attractions between oppositely charged ions are strong. |
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Molecular Solids |
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Consist of discrete molecules that occupy positions in unit cells. Intermolecular forces are relatively weak. London Forces and D-D. |
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Covalent Solids |
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Individual atoms are covalently bonded to several other atoms; thus they are very hard with very high melting points. Diamond, graphite, SO2 (sand), SiC. Molecular less than Metallic less than Ionic less than Covalent |
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Two major factors affect dissolution of solutes |
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Enthalpy and Entropy |
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Crystal Lattice Energy |
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Measure of attractive forces among particles of a solid. Increases as the charges on ions increase. The higher the CLE, the stronger the bond. |
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Enthalpy |
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Change of energy content of solution (ChangeHsoln). If change Hsoln is exothermic (<0), dissolution is favored. -changeH |
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Entropy |
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Change in disorder (randomness( of the solution. ChangeSmixing. NaCl --> Na+ + Cl- increasing entropy +changeS |
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Molality |
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mol solute/kg solvent |
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Molarity |
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mol solute/L solution |
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Mole Fraction |
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Xa=(# mols of A)/(# mols of A + # mols of B) |
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Percent by Mass |
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g solute/100 g solution |