HOMEWORK PROBLEM Fuel ConsumptionA HYDROGEN ECONOMY IN OUR FUTURE?Chrysler PULSESmart Car Hybrid VehicleChlorine Destroys Ozone but is not consumed in the processCrutzenMolinaRowlandPaul CrutzenHolland (The Netherlands)Max-Planck-Institute for ChemistryMainz, Germany1933 -Mario MolinaUSA (Mexico)Earth/Atmospheric/Planetary Sciences and ChemistryMIT1943 -Sherwood RowlandUSA Chemistry University of Californiaat Irvine 1927 -Three States of Matter• …. it is possible toexplain nearly all ofthe bulk properties ofgases, liquids, andsolids• …. it is possible toexplain the colligativeproperties ofsolutions.• By assuming theexistence ofattractive andrepulsive forces...• By assuming theexistence ofthermal energy...Ideal (Perfect) Gases ObeyBoyle’s Law for which PV = kIdeal (Perfect) Gases ObeyBoyle’s Law for which PV = k• HOWEVER, if you…– Increase P– Increase n in a given V– Lower the K.E. (T)THEN gas particles canCOALESEBUT before condensationoccurs, PV=nRT deviatesfrom ideal behaviorReal (van der Waals) gasesdeviate from ideal behaviorGases at 25°CN2 at different T PV = nRT(P + n2a/V2)(V - nb) = n RT PV = nRTCritical Properties of CO2Critical Conditions• Condensable GasesTcPc– NH3132 112– Cl2144 76– H2O 374 218• Permanent GasesTcPc– O2-118 50– N2-147 33.5– H2-239 12.8– He -267 2.3SIGNIFICANCE OF TCSIGNIFICANCE OF TC EVALUATE THERMAL vs POTENTIAL ENERGY Thermal energy Potential EnergyCHEMICAL BONDSIonic and Covalent Bonds (102)Salt (NaCl) and water (H2O)H-bonding Forces (100)Liquids and solutionsVan der Waals Forces (10-2)Instantaneous and permanentdipolar forcesThe Liquid State• Gases– Study is simplifiedby the facts thatatoms and moleculesare…• far apart.• randomly arranged.• weakly interacting.• Solids– Study is simplifiedby the facts thatatoms and moleculesare…• close together.• regularly arranged.• strongly interacting.The Liquid State• Gaseous state modelfor liquids:– Liquids as dense gasesare characterized by...• DISORDER• fluidity• taking the shape oftheir container• low density• Solid state model forliquids:– Liquids as disorderedsolids characterizedby….• ORDER• strong inter-atomic/molecularinteractions• definite volumes• high densityThe Liquid StateTrajectories for Atoms atLattice Points in SolidsThe Liquid StatePhase Diagram for CO2Phase Diagram for H2OThe Liquid State• Vapor pressure• Surface tension• Viscosity• Adhesive/cohesiveforces• Capillary action• Density• Compressibility• Diffusion• EvaporationDensity of Ice and WaterCompressibilitySurface TensionEquilibrium Vapor PressureVapor Pressure CurvesTrouton’s RuleAn interesting and useful “approximation:• Says that the ratio of the heat of vaporization and the boiling point is (roughly) constantDHvap/Tb.p. ~ 88 J/mol• Boiling point of cyclohexane is 69°C. Therefore, DHvap = (69 + 273)(88) ~ 30 kJ/mol which is within 2-3% of the experimental value• Works well for unassociated liquids and gives useful information about degree of association.Trouton’s RuleUnassociated (ideal) liquids, DHvap/Tb.p. ~ 88 J/molcarbon tetrachloridebenzenecyclohexaneAssociated liquids, DHvap/Tb.p. > 88 J/molwater (110)methanol (112)ammonia (97)Association in the vapor state, DHvap/Tb.p. < 88 J/molacetic acid (62)hydrogen fluoride
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