chem. 412 – phys. chem. i

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Chem. 412 – Phys. Chem. I. Free Energy Comparisons. Free Energy Comparisons - I. Free Energy Comparisons - II. Free Energy Comparisons - III. Free Energy Comparisons - IV. Free Energy Comparisons – I – F12. Free Energy Comparisons – II – F12. Free Energy Comparisons – III – F12. - PowerPoint PPT Presentation

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  • Chem. 412 Phys. Chem. I

  • Free Energy Comparisons

    Helmholtz F.E. (A)Gibbs F.E. (G)A = U - TSG = H - TS@Cont.T=> Asys= Usys - T Ssys@Cont.T=> Gsys = Hsys - T SsysIf Asys< 0, rxn spontaneous. (Constant V & T)If Gsys< 0, rxn spontaneous. (Constant P & T)If Asys = 0, rxn @ equilibrium.If Gsys= 0, rxn @ equilibrium.dA = -PdV SdTdG = VdP - SdT

  • Free Energy Comparisons - I

  • Free Energy Comparisons - II

  • Free Energy Comparisons - III

  • Free Energy Comparisons - IV

    Helmholtz F.E. (A)Gibbs F.E. (G)A = U - TSG = H - TS@Cont.T=> Asys= Usys - T Ssys@Cont.T=> Gsys = Hsys - T SsysIf Asys< 0, rxn spontaneous. (Constant V & T)If Gsys< 0, rxn spontaneous. (Constant P & T)If Asys = 0, rxn @ equilibrium.If Gsys= 0, rxn @ equilibrium.dA = -PdV SdTdG = VdP - SdT

  • Free Energy Comparisons I F12

  • Free Energy Comparisons II F12

  • Free Energy Comparisons III F12

  • Free Energy Comparisons III F11*

  • Phase Diagrams

  • The Phase Diagrams of H2O and CO2Phase Diagrams

  • Phase Transitions: Clapeyron Equation

    Over moderate temperature ranges:

  • Phase Transitions: Clapeyron Equation I F14

  • Phase Transitions: Clapeyron Equation II F14

  • Phase Transitions: Clapeyron Equation III F14

  • Phase Transitions: Clapeyron Equation I F13

  • Phase Transitions: Clapeyron Equation II F13

  • Phase Transitions: Clapeyron Equation III F13

  • Application of Clapeyron EquationConsider:Ice Water (ice, 101 kPa, 273 K) = 0.917x103 kg m-3 (liq, 101 kPa, 273 K) = 0.988x103 kg m-3

    Hf = 6.01 kJ mol-1 ( s liq )

    Triple point at 0.6 kPa and 273.16 K

    What is the melting point at 1.5x105 kPa ( 1500 atm ) ? Application: Blade in Ice-Skating.Mathcad Key

  • Clausius-Clapeyron EquationApplicable only to:s g & liq g equilibria

    Integrated form:

    Indefinite Integrated form:

    T-dep form:

  • Clausius-Clapeyron Equation - I

  • Clausius-Clapeyron Equation - II

  • Clausius-Clapeyron Equation I F11*

  • Clausius-Clapeyron Equation II F11

  • Standard States & GorxnPofor gas:ideal gas; Po = 101.325 kPa non-ideal gas; (leave for now) for liquid:pure liquid at Pofor solid:most stable crystalline structure at Po

    To for all substances:298.15 K exactlySoo = 0 at 0 K for pure crystals

    Hof(To) = 0 for elements at reference state

    G convention must follow that of H & S

    Grxn from formation values

  • SubstanceHf (kJ/mol)Gf (kJ/mol)S (J mol-1 K-1)C(s, diamond)1.882.842.43C(s, graphite)005.69

  • P/T-Dependent EquationsVariation of G with P for an ideal gas:

    Variation of G with T:

    Variation of KP with T:

  • P/T-Dependent Equations

  • A = U - TSG = H - TSIf Asys< 0, rxn spontaneous. (Constant V & T)If Gsys< 0, rxn spontaneous. (Constant P & T)dA = -PdV SdTdG = VdP - SdT

    **************

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