L21S10_RealGases,+PhaseTransitions+03-10-10 - CHEM 1A...

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Unformatted text preview: CHEM 1A L21: "Real Gas Behavior, Phase Diagrams" Summary © 2004 M. Kubinec L21-1 Distribution of Speeds vrms F(v) vrms MaxwellMaxwell-Boltzmann High T Low T F(v) proportional v2 e Low m High m -E/kBT v (ms-1) © 2004 M. Kubinec L21-2 ChemQuiz© 20.4 Shown is the MB F(v) distribution at ~300 K for Br2 and X. What is X? Wh X? Br2 vrms X vrms v Molar Mass Ne Ar Br Kr 20 40 80 83 A) Ne © 2004 M. Kubinec B) Ar C) Kr L21-3 © 2004 M. Kubinec 1 CHEM 1A L21: "Real Gas Behavior, Phase Diagrams" Real Gas Behavior P Summary V ΔP Tc V V =- 1 ΔV V P Ideal: PV=const © A.Pines,M.Kubinec,UCB Real: PV = ? L16-21 © 2004 M. Kubinec L21-5 Ideal Gas Behavior P =- 1 ΔV V ΔP Ideal Gas: Decreasing Compressibility Ideal: PV=const © 2004 M. Kubinec V P1 < P2 < P3 < P 4 L21-6 Real Gas Behavior P Real Gas: Phase Transition Tc V P1 Real: PV = ? © 2004 M. Kubinec < P2 = P3 < P4 L21-7 © 2004 M. Kubinec 2 CHEM 1A L21: "Real Gas Behavior, Phase Diagrams" ChemQuiz© 21.1 P Which is true of the critial temperature,Tc temperature,T for any real gas ? real Tc V A) < ideal gas B) = ideal gas C) > ideal gas © 2004 M. Kubinec L21-8 Real Gases: Vapor Pressure P(atm) Vapor Pressure Water 1.000 0.031 Tc 100 oC 25 oC V L21-10 © 2004 M. Kubinec Intermolecular Forces DipoleDipole-Dipole +H H O - +H H O - Transient / Induced Hydrogen Bonding © 2003 M.Kubinec,UC Regents δ+ δ- δ+ δ- HO+ H H O H L21-11 © 2004 M. Kubinec 3 CHEM 1A L21: "Real Gas Behavior, Phase Diagrams" Van der Waals Equation P+a n2 V2 V - nb =nRT a: adjust ‘P’ for collisions/attractions b: adjust ‘V’ for finite volume of molecules He CO2 H2O © 2004 M. Kubinec a 0.034 3.59 5.46 b B.P. (K) 0.024 4.2 0.043 0.030 195 373 L21-12 CO2 S P Phase Diagram L Triple Point TTP = -56.6 oC PTP = 5.1 atm G Temperature Tc L21-13 © 2004 M. Kubinec ChemQuiz© 21.2 Which plot corresponds to the process shown ? P S L G P P P T Tc A) B) V V C) V L21-14 © 2004 M. Kubinec © 2004 M. Kubinec 4 CHEM 1A L21: "Real Gas Behavior, Phase Diagrams" H2 O S P G Temperature © 2004 M. Kubinec Phase Diagram L Triple Point TTP = 0.01 oC PTP = 4.6 torr Tc L21-16 ChemQuiz© 21.3 Solution P S L G P P T Tc P A) T © 2004 M. Kubinec B) T C) T L21-18 ChemQuiz© 21.4 Which is the 373 K isotherm for water ? P S ABC L G T Tc A) A © 2004 M. Kubinec B) B C) C L21-19 © 2004 M. Kubinec 5 CHEM 1A L21: "Real Gas Behavior, Phase Diagrams" Lecture Complete © 2004 M. Kubinec L21-21 © 2004 M. Kubinec 6 ...
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This note was uploaded on 04/24/2010 for the course CHEM 1A taught by Professor Nitsche during the Spring '08 term at Berkeley.

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