Ch9 - Thermodynamics Kinetics The study of energy & its...

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Unformatted text preview: Thermodynamics Kinetics The study of energy & its transformations Energy content of reactants & products Enthalpy Heat content Entropy Disorder Will the rxn happen? Section 9.0 How fast & by what mechanism will the reaction occur? H 2 + 1/2 O 2 b H 2 O nergy released = -237 kJ Thermodynamics predicts that the reaction is favorable. (negative E) However, no reaction is observed when H 2 and O 2 are mixed. THERMODYNAMICS Once a small amount of energy is added (spark) the reaction proceeds! KINETICS Section 9.1 Energy is neither created nor destroyed in any process. The form of the energy can change in a process. Heat: disorganized energy something we feel Work: organized energy something we see E system = q + w Heat: disorganized E Work: organized E E univ = E system + E sur = ZERO q > 0: heat is absorbed by the system q < 0: heat is released from the system Section 9.1 w > 0: work is done on the system w < 0: work is done by the system E system = - E sur E univ = E system + E sur = ZERO When the system absorbs E, the surroundings must release E. When the system releases E, the surroundings must absorb E. Section 9.1 When the system absorbs E, the surroundings must release E. system Section 9.1 Solid Gas E in System Energy CO 2 (s) CO 2 (g) When the system absorbs E, the surroundings must release E. surroundings Section 9.1 Surroundings Energy E out Liquid Gas CO 2 (s) CO 2 (g) H 2 O (g) H 2 O (l) When the system absorbs E, the surroundings must release E. surroundings Section 9.1 Potential Energy CO 2 H 2 O (g) E out Liquid Gas Solid Gas E in system CO 2 (g) When the system absorbs E, the surroundings must release E. Section 9.1 Potential Energy Solid Gas E in CO 2 E out Liquid Gas H 2 O E univ = E system + E sur E univ = ZERO An appropriate number of molecules of H 2 O are condensing, compared to the molecules of CO 2 that are subliming, Such that E univ = ZERO E system written as E in text Section 9.1 Chemical rxn or phase transformation under study A system has 200 J of work done on it And releases 125 J of heat. What is E system ? E system = q + w E system = What is E sur ? E sur = - E system = What is E univ ? ALWAYS, ALWAYS ZERO Section 9.1 E system = q + w Heat transferred: disorganized E E univ = E system + E sur = 0 Section 9.2 E = q = H Work: organized E Constant P Enthalpy Endothermic process: a process in which heat is absorbed into the system. H system = - H sur E univ = E system + E sur = 0 Exothermic process: a process in which heat is released from the system. Section 9.2 E = q = H @ constant P When the system is undergoing an e x o t h e r m i c process, the surroundings must be undergoing an e n d o t h e r m i c process. Endothermic (from the systems perspective) surroundings i H > 0 H = H prod- H react We (as part of the surroundings) perceive endothermic processes...
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This note was uploaded on 03/29/2008 for the course PSY 200 taught by Professor Craig during the Spring '08 term at N.C. State.

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Ch9 - Thermodynamics Kinetics The study of energy & its...

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