Chapter 6 notes

Chapter 6 notes - Chapter 6 Objectives(Thermochemistry 1...

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Chapter 6 Objectives (Thermochemistry) Spring 2084/Chem 0970 1. Introduction. a) Thermochemistry is the measurement of and study of how energy interacts with chemical systems. b) The study of thermochemistry and energy in general resulted in the first law of thermodynamics. 1. Energy is neither created nor destroyed in chemical reactions or physical systems; ΔE = q + w (first law of thermodynamics) 2. That is, heat, work, and energy are interconverted during physical or chemical changes. q is heat released (-) or absorbed (+). w is work done by the system (-) or on the system (+). Δ e is the change in internal energy. 3. Although work in a chemical reaction can be derived electrically, it is commonly done by the expansion of a gas (from the reaction) against the atmosphere and is expressed as PΔV. ΔE = q + PΔV. 4. IF ΔV = zero, as in a closed system, ΔE = q v and can be measured in a constant volume calorimeter. 5. For reactions done at constant pressure on the lab benchtop, q is defined as enthalpy or ΔH. Thus, ΔE = ΔH + PΔV. 6. ΔE and ΔH are thermodynamic functions of state which means that they are independent of path. For example, for C + O 2(g) (state 1) CO 2(g) (state 2) ΔH is -393.5 kJ, thus C (s) + 1/2 O 2(g) CO (g) ΔH 1 CO (g) + 1/2 O 2(g) CO 2(g) ΔH 2 C (s) + O 2(g) CO 2(g) ΔH 1 + ΔH 2 ≡393.5 kJ 7. ΔH for a reaction can be measured in a constant pressure calorimeter.
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This note was uploaded on 04/07/2008 for the course CHEM 0970 taught by Professor Kogut during the Spring '08 term at Pittsburgh.

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Chapter 6 notes - Chapter 6 Objectives(Thermochemistry 1...

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