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090130_lecture8

# 090130_lecture8 - Physical Chemistry I for Biochemists...

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1 Physical Chemistry I for Biochemists Chem340 Lecture 8 (1/30/09) Yoshitaka Ishii Ch. 2.8-10 (Skip printing p2-4 if you have lec. note 7) Derivative & Partial Derivatives Intro of Ch3. HW3 Announcement We will start a study group from next Monday right after the class. Quiz 1 will be held in the discussion class. ACCC reported that they fixed problems related to printing of pdf files. If you still find problems, report it to [email protected] with specific problems and information on the site and computer you used.

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2 2.8 Determining Δ U & Introduction of Enthalpy H : a New State Function (1) Relationship between U and q under a constant V If w= PdV = 0, Δ U = q Æ Δ U can be determined by heat under a constant V as (2) What about it if P = const? Δ U = q + w = Δ U = q - P ext Δ V Æ q = Δ U + P ext Δ V (3) Let us define H as (4) Relationship between H and q under a constant P int Δ U V = q v H U + P int V Δ H P = Δ U + P Δ V = q p (for reversible process) 2.9 Calculating q, w , Δ U, Δ H for Ideal Gas (Note: all the equations in this section of the text are valid only for Ideal Gas) ) ( ) ( ini fin V T T V V T T C dT T C q U fin ini = = = Δ H T T C dT T C q ini fin P T T P P fin ini Δ = = = ) ( ) ( T C T nR C T nR T C T nR U nRT U PV U H p V V Δ = Δ + = Δ + Δ = Δ + Δ = Δ + Δ = Δ + Δ = Δ ) ( ) ( ) (