EXAM I STUDY GUIDE CHAPTERS 11-13CHAPTER 11: INTERMOLECULAR FORCES + PHASESThe kinetic molecular theory States that energy comes from temperatureGases: gases are governed by this theory with assumptions that it is an ideal gas where distance between atoms is big, the gas has free motion and is temperature dependent Liquids/Solids: depends of 2 major parts-temperature and intermolecular forcesIntermolecular forces vs. intramolecular forcesIMF: forces between molecules (more than 2 molecules) Intra- hold a single molecule together; much stronger than IMFDifferent types of intermolecular forces (IMFs)Van der waals (dipole-dipole, dipole-induced dipole, London dispersion forces),electrostatic forces (dipole-ion attraction), hydrogen bondingDipole-dipole Results from molecules having a dipole moment (different electonegativites/polar molecule); creates stability because the negative part of one molecule lines up with the positive part of another and holds them together Dipole-induced dipole Between nonpolar molecules and a polar molecule; the non polar molecules, when lined up with the polar, create a diffrent electron cloud distribution and an induced dipole is formed (either negative or positive depending on where the molecule is relative to the polar molecule)Greater number of electrons = easier to polarizeLondon dispersion forcesTemporary forces created by movement of electrons (predominant in nonpolar molecules)Weakest of the IMFsMost occurring (all have this) and can also be additive Happens because all electrons have free flowing motion and when they move they have brief interactions with other molecules Ion-dipole attraction Attraction of an ion and a polar moleculeEx. is hydration when an ion is surrounded by water molecules and attracted to the positive end of the polar molecule when an anion and the negative end of polar molecules when a cationHydrogen bonding Strong IMF between the H atom in a polar bond and an O,N, or F atom that hasa lone pairMore hydrogen bonds a molecule has the higher the boiling pointSurface tension Amount of energy required to increase the surface of a liquidStronger IMFs = stronger surface tensionCohesion Attraction to similar moleculesAdhesion Attraction to different moleculesViscosity Measure of a fluid’s resistance to flow-usually changes with temperatureStronger IMF = higher viscosityA high viscosity means it does not flow wellPhase change Transformation from one phase to another Usually energy is added or removed from a substancePhysical changes characterized by changes in molecular orderEXAM I STUDY GUIDE CHAPTERS 11-13Evaporation/vaporizationWhen molecules of a liquid have enough energy to break from their IMFs the liquid changes to a gasLIQUID TO GASMore temperature= greater kinetic energy= more molecules leave the liquid and turn into gasCondensation When a gas converts back to a liquidGAS TO LIQUIDVapor pressure Depends on 2 things: temp and IMFsVapor pressure: pressure exerted on solution by molecules that a evaporatingDynamic equilibrium Rate of forward reaction = rate of reverse reaction Ex. rate of evaporation = rate of condensation Molar heat of vaporizationEnergy required to vaporize 1 mole of a liquid The strength of the IMFs can be predicted using this; the stronger the IMF = the higher the ∆Hvap which means it is hard to vaporize Equations to find this/ Clausius-Clapeyron equationLn P = (-∆Hvap/RT) + CWhere R is gas constant 8.134 J/mol*K and C is a constant Use this equation when graphing in y=mx+b format where y= ln P, m= (-∆Hvap/R), x= 1/T and b= CPlot ln P vs. 1/T and the slope will equal (-∆Hvap/R) will also give a straight lineSteeper the slope = higher value of delta HvapAnother equation to use:When you have 2 temperatures/pressuresLn (P1/P2) = (∆Hvap/R)*(1/T1 – 1/T2) orLn (P1/P2) = (∆Hvap/R)*((T1-T2)/(T1*T2))Boiling point Temperature where vapor pressure = external pressureHigher IMF = higher boiling pt2 ways to condense a gasReduce the temp and raise the pressure but there are 2 important conditions that coincide with this- Critical temperature (TC)Temp where a gas cannot condense Temp is so high it will not form and condense no matter how strong the IMFs - Critical pressure (PC)Minimum pressure that can condense a gas near TcThis is right below the point of Tc; min pressure to make it condense until it won’t condense any more when it reaches the actual TcMelting point Temperature of solid to liquid conversionFreezing point Temperature for liquid to solid conversionHeating curve Illustrates heat (energy) added and the temperatureEXAM I STUDY GUIDE CHAPTERS 11-13Molar heat of fusion Energy required to melt one mole of a solid∆HfusSublimation SOLID TO GASDeposition GAS TO SOLIDMolar heat of sublimation ∆Hsub energy required to sublime 1 mole of a substance ∆Hsub = ∆Hfus + ∆Hvap-for problems that you need to use this concept you have to use the heat equation q=ms∆T for the different phases in the problem Phase diagram Visual summary of the conditions at which a substance exists in the various phasesWhen you cross a line it is a phase change Triple point Only condition under which all phases can be in equilibriumWhere all three curves intersectEXAM I STUDY GUIDE CHAPTERS 11-13CHAPTER 12: SOLUTIONSLiquid/gas, liquid/solid, liquid/liquid; saturated, supersaturated, unsaturatedSaturated Contains the max amount of solute that will dissolve in a solvent at a specific temperature -All solute you are allowed to use-Unsaturated Contains less solute than it has capacity to dissolveSupersaturated Contains more solute than is present in a saturated solution-very unstable Crystallization When a dissolved solute comes out of solution (supersaturated) and forms a crystal Solute What is dissolved in a solutionSolvent Dissolves the solute3 interactions for a solution Solute-solute, solute-solvent, solvent-solvent Solution is governed by 2 things:Energy and disorder/randomnessEnergy The ∆H of spontaneous reactions are negativeDisorder/randomness When a solute and solvent are mixed, much of the order/organization is disrupted this increase in disorder (entropy) favors the solubility of any substanceIMFs vs. Solubility “Like IMFs dissolve like species” this means that two substances are more likelyto interact if their IMFs are similar Miscible Substances that are completely soluble in each other in all proportions; no saturation pointConcentration Amount of solute present in a given solutionWays to
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