CHEM 112 EXAM 2CHAPTER 11Intermolecular Forces: Exist between two molecules (will not be dealing with INTRAaka ionic covalent…)- IMFs directly relate to physical properties (boiling point melting point etc)- Gas  weak IMFs  high compressibility- Liquid  intermediate IMFs  low compressibility- Solid  strong IMFs  no compressibilityFusion (melting) solid  liquid endothermicVaporization liquid  gas EndothermicSublimation (dry ice) Solid  gas EndothermicFreezing Liquid  solid ExothermicCondensation Gas  liquid ExothermicDeposition Gas  solid exothermic- Endothermic – goes from a more ordered state to a less ordered state (solid  liquid/gas)- Exothermic – less ordered state to more ordered stateEnthalpy of vaporization deltaHvap = energy required to change 1 mol of a liquid to a gas at a certain temperature- AS THE STRENGTH OF THE IMFs IN A SERIES OF LIQUID INCREASE, THE ENTHALPY OF THE VAPORIZATION VALUES FOR THE LIQUIDS ALSO INCREASE- The higher the equilibrium vapor pressure, the more volatile the molecule, the lower the boiling point- VAPOR PRESSURE INCREASES WITH INCREASING TEMPERATURE- When equilibrium is reached, evaporation does not stop; it’s when the rate of evaporation and condensation are equal- “…does all the liquid evaporate?”  use PV=nRT- if p < vp, yes all liquid evaporates- if p>vp, no all liquid does not evaporateBoiling point- when VP equals exactly atmospheric pressure- When vp exactly equals atmospheric pressure of 1 atm, this is known as the normal boiling point- When liquid boils, the strength of IMFs are overcome- THE HIGHER THE EQUILIBRIUM VP, THE LOWER THE BPFOR A LIQUID, AS IMF STRENGTH INCREASES:- The energy needed to vaporize the liquids (deltaHvap) will also increase- The equilibrium VP decreases and consequently the liquid normal boiling point increasesSTONG IMF  HIGH deltaHvap  LOW VP  HIGH BPClausius Clapeyron equation relates the pressure, temp, and strength of IMFs- Mainly used for calculating deltaHvap- MAKE SURE TO USE KELVIN!!!!!!!!Surface Tension- the toughness of a liquid skin- Molecules at surface behave differently than those in the interior- S.T is the energy required to break through the surface- Different molecules have different surface tensions- Addition of soap to water changes the surface tensionCapillary Action- the forces between molecules and external devices- When a glass tube with a small diameter is placed in water, the water rises bc CapAction; meniscus- Water molecules are attracted to the glass surface by hydrogen bonding, some water molecules adhere to the glass while others attract to other water moleculesLower vp  higher bpStrength of IMFs is directly dependent on differing charges of interacting atoms; the strength follows Coulombs Law, which relates electric charge and distanceForce is proportional to (qA)(qB)/r^2q being lowercase delta being partial chargeDipole-Dipole – in POLAR moleculesWhy does O2, a nonpolar molecule, dissolve in H2O?  Dipole- Induced Dipole** Inducing a dipole form a seemingly nonpolar substance is called polarization- THE GREATER THE MOLECULAR WEIGHT, THE MORE POLARIZABLE  STRONGER INDUCED DIPOLE IMFLondon Dispersion Forces (LDF) – IN EVERYTHING- Induced dipoles in 2 nonpolar molecules—WEAKEST INTERACTION- ONLY IMF PRESENT IN NONPOLAR MOLECULESAs you go further down the periodic table, the more polarizable molecules becomeHydrogen Bonding- polar with O, N, or F – nothing else- must be directly connected- THE MORE HYDROGEN BONDING POTENTIAL THE HIGHER THE BPCHAPTER 13Solvent- the liquid doing to dissolvingSolute- the compound being dissolvedUnsaturated Solution- one that can dissolve more soluteSaturated- one that cannot dissolve more soluteSupersaturated- one that contains more dissolved solute at a given temperature; very unstableElectronegativity- low at bottom left corner of periodic table, gets higher towards top rightCohesive Forces- attractive forces that exist between molecules at the macroscopic level that affect the physical properties of a liquid- Sometimes called bulk-scale forces; result of IMFs, the molecular level interactions in a liquidEntropy- the measure of disorder of a system, also known as molecular randomness or freedom of molecular motion- Increasing temperature increases entropyEnthalpy change- the difference between the strength of a substances IMFs and the interaction between the solute and the species in the solution+ Enthalpy ChangeEndo- Enthalpy ChangeExoIncrease in disorder+ Entropy change Favored at high tempsFavored at all tempsDecrease in disorder (more organized state)- Entropy change Not favored at any tempFavored at low temps** Flow chart in notesMiscible- if 2 liquids mixImmiscible- if 2 liquids do not mix- Whether or not the liquids are miscible also depends on entropy and enthalpy “LIKE DISSOLVES LIKE” ie: polar substances dissolve nonpolar substancesThe greater the dipole moment, the stronger the IMFThe greater the ions charge, the stronger the IMFBoiling Point Elevation- the addition of a solute will LOWER the VP, but INCREASE the NBP- The solutions (which has a NBP) will need to be heated to a higher temperature in order for the VPsoln to become equal to the atmospheric pressureTbp = Kbp miTbp- change in BP of solventKbp- BP elevation constantm- molality of solutioni- Van’t Hoff factor; essentially 1 for nonelectrolyte solutionsFreezing Point Depression- solutes will lower the freezing point of the pure solventTfp = Kfp miKfp- freezing depression constant; ALWAYS NEGATIVETf(solution)=Tf(solvent)-deltaTf=KKfmiOsmotic Pressure- Pi = MRTiM= molarityR= 0.082057 ATM/mol KT= temp IN KELVINI= Van’t Hoff FactorHydration number increases with decreasing charge and decreasing radius; smaller, highly charged ions have very large hydration numbersHydration enthalpy increases in magnitude as the ion charge increases and as radiusdecreasesThe smaller the hydration number, the more favored the dissolution in terms of entropy; low charge large radiusEnthalpy of Solvation- the energy associated with dissolving ions in a solvent; when a solvent is water, called enthalpy of hydration- Can be endo or exoAS IONS BECOME LARGER, THE INTERACTIONS BECOME WEAKER; solvation is less exothermic with larger ions- Solids dissolving in liquids- temp is only factor- Gases dissolved in liquids- both pressure and temp are factorsDissolved Gasses and Henry’s LawSg=KhPgSg= gas solubilityKh= Henry’s