Recitation-08

Recitation-08 - Chemistry 111 Chemistry 111 Recitation 8...

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Chemistry 111 Fall, 2005 Prof. Simpson Chemistry 111 Recitation # 8 November 8, 2005 Where have we been with Thermodynamics ? Thermodynamics intro – lots! of definitions. (ick. know them.) Thermodynamics is about which reactions will go Æ Energy is the key Æ work and heat are ways to pass energy from place to place E = internal energy Δ E = q + w Å The First Law of Thermodynamics w = 2 1 V ext V PdV q = n C Δ T H = enthalpy = E + PV Δ H = Δ E + Δ (PV) Ideal Gases . q V = n c V Δ T = Δ E q P = n c P Δ T = Δ H Isothermal Processes . Δ E = Δ H = 0 expand irreversibly against a vacuum … w = 2 1 V ext V = 0 q = Δ E – w = -w expand irreversibly against a constant external pressure … w = 2 1 V ext V = - P ext Δ V q = Δ E – w = -w reversibly (P ext = P gas during the whole process) … w = 2 1 V ext V = 22 11 ln ln VP nRT ⎤⎡ −= ⎥⎢ ⎦⎣ q = Δ E – w = -w Isochoric Processes Constant External Pressure Processes w = 2 1 V ext V = 0 w = 2 1 V ext V = - P ext Δ V Δ E = q V + w = q V = n c V Δ T Δ E = q + w = n c V Δ T Δ H = n c P Δ T Δ H = q P = n c P Δ T Thermochemistry – heat and chemical reactions Æ enthalpy changes ( Δ H rxn ) for reactions and Hess' Law Æ standard state Æ standard enthalpies of formation Hmmm … since work (w) and heat (q) are not state functions we can't really write down any useful general equations … their value depends on
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This note was uploaded on 02/08/2010 for the course CHEM 111 taught by Professor Kenney during the Spring '08 term at Case Western.

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Recitation-08 - Chemistry 111 Chemistry 111 Recitation 8...

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