CH204 Expt 8 thermochemistry sp10

CH204 Expt 8 thermochemistry sp10 - Thermochemistry...

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1 Experiment 7 Thermochemistry Thermochemistry The study of heat in chemical reactions. Heat is produced and consumed in chemical reactions in stoichiometric amounts, just like any other reactant or product. Thermochem in CH204 We look at two different thermochemical situations: Calorimetry add something hot to something cold heat lost by the hot = heat gained by the cold Hess’s Law Forming chemical bonds releases energy. Breaking chemical bonds requires energy. Add up all the energies to get the heat of reaction, H rxn . Calorimetry Calorimeter – a container that traps heat Put a known mass of water in the calorimeter, add something hot, and measure heat gain by the temperature increase of the water The calorimeter itself also heats up when something hot is added Accounting for heat energy The total amount of heat added is equal to the amount of heat absorbed by the water plus the amount of heat absorbed by the calorimeter: q added = q water + q calorimeter The amount of heat absorbed by the water is equal to the mass of the water times the change in temperature times its specific heat capacity: q water = m w × C × T The amount of heat absorbed by the calorimeter is equal to its heat capacity times the change intemperature: q cal = C cal × T Specific heat capacity The amount of heat it takes to raise 1 gram of a substance by 1 degree C or one Kelvin. (under constant pressure) Units are J/g·K
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2 A word on heat capacities SPECIFIC HEAT CAPACITY is an intensive property. Specific heat capacity tells how much heat (in Joules)
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This note was uploaded on 12/21/2010 for the course CH 204 taught by Professor Leytner during the Spring '08 term at University of Texas at Austin.

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CH204 Expt 8 thermochemistry sp10 - Thermochemistry...

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