SLec10m - Lecture 10: Experimental Thermochemistry...

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Typically, reaction heats are measured by one of the following methods: In direct calorimetry , the reaction proceeds at dV= δ w=0 in a bomb (see picture) and at δ q=0 (insulation), so that Δ U Total =0 We measure the change of temperature of the water surrounding the bomb and from the heat capacities calculate the heat produced in the reaction (= Δ U R + absorbed heat) We can either measure directly the heating or heat the system electrically to compare the heats We first calibrate the system in a known reaction to find the heat capacity of the calorimeter Then, we do other reactions with known amounts of reactants and products (heat capacities) to find their reaction heat The comparative method is more precise Lecture 10: Experimental Thermochemistry
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In differential thermal analysis (DTA), the measurement is done in a time dependent way, where we use sample and reference cells (see picture) The heat produced in the sample in time dt heats it and the bath. The balance is , while in the reference cell
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This note was uploaded on 09/23/2010 for the course CHEM 342 taught by Professor Prestonsnee during the Spring '08 term at Ill. Chicago.

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SLec10m - Lecture 10: Experimental Thermochemistry...

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