4-EnergyCycles

# 4-EnergyCycles - Assignments Competency Quiz Ice Water and...

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Assignments Competency Quiz Ice, Water and Steam Problem Set Internal Energy, Heat & Work

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Calorimetry and Energy Cycles Edward A. Mottel Department of Chemistry Rose-Hulman Institute of Technology
Topics Reading assignment: Chang: Chapter 6.4-6.5, 11.8 This lecture describes calorimetric methods to measure heat flow. an application of the conservation of energy by using energy cycles to solve a thermodynamic problem. the calculation of work performed by an expanding gas for various pathways.

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Calorimeter q system + q surroundings = 0 GOAL: limit heat gain of surroundings to zero An insulated device in which reactants are mixed together, and the change in temperature of the products and the calorimeter is used to calculate the heat of reaction.
Constant Pressure Calorimeter Adiabatic calorimeter q = 0 No heat flow between system and surroundings System: reactants and part of calorimeter touching the reactants Surroundings: everything else q Vacuum or insulated space Thermometer

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Energy Balance q system + q surroundings = 0 q solution + q calorimeter = 0 0
Constant Pressure Calorimeter Any heat released is trapped by the solution and calorimeter unit. No heat is transferred to the surroundings. The heat flow in this process is equal to which thermodynamic term, q p or q v ? = 0 + (m solution . C p,solution · T) (C calorimeter · T) q solution + q calorimeter = 0

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Constant Pressure Calorimeter Example A steel bolt (17.93 g) is heated in a Bunsen burner flame for four minutes. The bolt is placed in 209 mL of water at 19.1 °C. The temperature of the water rises to 26.0 °C. The heat capacity at constant pressure for iron is 0.444 J·g –1 · K –1 . What is the temperature of the hot bolt?
Constant Volume Calorimeter Oxygen Bomb Calorimeter A thick walled device in which a reactant is combusted in air or oxygen. Heat flows from the device to its immediate surroundings, and the temperature change of these surroundings is used to determine the heat of reaction.

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Oxygen Bomb Calorimeter Thermometer water Ignition source
Constant Volume Calorimeter Oxygen Bomb Calorimeter The water surrounding the reaction container behaves as a large heat sink.

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