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Unformatted text preview: CH101/Ison Name: ___________, __________ Ch9 Thermodynamics I. Energy : Energy is constantly exchanged between the system and the surroundings, where E universe = E system + E surroundings = 0 E system = - E surroundings 1. If the system gives off energy, what do the surroundings do with that energy? The surrounding will absorb the energy given off by the system. E system = - E surroundings II. Heat and work: Heat (q) and work (w) are the most common ways to exchange energy between the system and surroundings. E system = q + w (+) q: heat is absorbed by the system: ENDOTHERMIC (-) q: heat is released by the system: EXOTHERMIC (+) w: work is done on the system (-) w: work is done by the system Practice problems: 1. If we assume that a hot pack is the system, what is the sign of q? The hot pack feels hot to out hand (surroundings) because the system is giving off energy (heat) so q is negative. 2. What is the energy change of a system that absorbs 500J of heat and does 300J of work? If the system absorbs heat, q is positive. If the system does work, w is negative. SoE system = +500J + (-300J) = 200J III. Enthalpy or heat of reaction (H): The heat transferred in a chemical reaction (constant P) is the enthalpy or heat of reaction, H The answer to this question is in Ch9 slides. Energy Reaction coordinate Energy Reaction coordinate EXOTHERMIC ENDOTHERMIC Energy Reaction coordinate Energy Reaction coordinate Energy Reaction coordinate Energy Reaction coordinate EXOTHERMIC ( - H) ENDOTHERMIC (+ H) Energy Reaction coordinate Energy...
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- Spring '08