Handout2_Chapter7 - U rxn = heat + expansion work b. Bomb...

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Chemistry 008 Handout #2 Dr. Neal Abrams brought to you by the Spring 2007 Learning Strategies Center NOTE: This review sheet is for Chem 008 attendees and is to be used in conjunction with lecture notes, handouts, problem sets, the textbook, the laboratory manual, and notes from Chem 008. Chapter 7 Review Guide Lectures 1/30 and 2/1 I. Calorimetry a. Exothermic reactions: heat given off from system, q rxn <0 b. Endothermic reactions: heat is absorbed by the system, q rxn >0 c. Since the walls of a calorimeter are insulated, q rxn + q calorimeter = 0 d. q calorimeter = C calorimeter X Δ T II. Types of Energy Release a. Heat b. Light (rare) c. Work: Usually expanding gas molecules do work on their surroundings i. w = Force x Distance (h) ii. In a piston, F = P ext. x Area iii. w = -P ext. x Area x h = -P ext. X Δ V III. Enthalpy of a Reaction (H) a.
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Unformatted text preview: U rxn = heat + expansion work b. Bomb Calorimeter: i. Volume is constant, so Δ V = 0, so w = 0 ii. ∆ U rxn = q v iii. Heat of reaction is the internal energy c. Coffee Cup Calorimeter: i. Most reactions are at constant pressure (subscript p) ∆ U rxn = q p + w p ii. w = -P ∆ V, ∆ U rxn = q p- P ∆ V and rearranging gives q p = ∆ U rxn + P ∆ V iii. Enthalpy (H) is the measure of heat flow experienced by a system at constant pressure. q p = ∆ H = ∆ U + P ∆ V. iv. Enthalpy and energy are state functions. Only the initial and final states, but not the pathway, are of interest. v. Heat of reaction is the enthalpy. d. Standard State: Superscript ° i. P = 1 bar (1 atm. = 1.01325 bar) ii. T = 25 ° C (same as 298.15 K) iii. ex. Hg (l), H 2 O (l), Al (s), O 2 (g)...
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This note was uploaded on 05/18/2008 for the course CHEM 2080 taught by Professor Davis,f during the Spring '07 term at Cornell University (Engineering School).

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