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Calorimetry

Calorimetry. General Chemistry 101/102 Laboratory Manual University of North Carolina at Wilmington. Safety and Waste Management. Exercise care when handling objects that have been heated. Remove the stopper from the test tube when heating your metal sample ( never heat a closed system! )

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Calorimetry

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  1. Calorimetry General Chemistry 101/102Laboratory ManualUniversity of North Carolina at Wilmington

  2. Safety and Waste Management • Exercise care when handling objects that have been heated. • Remove the stopper from the test tube when heating your metal sample (never heat a closed system!) • Dry your metal sample before returning it. Calorimetry • Purpose • To learn techniques for measuring changes in thermal energy (heat) in substances. • To examine the relationship between the specific heat capacity of a metal and its atomic weight.

  3. (1) q = s x g x DT mass of substance (in grams) specific heat capacity of substance (J/gºC) temperature change (in ºC) heat transferred(in joules) Calorimetry • Background • The thermal energy (q) transferred when an object is heated or cooled can be calculated from the following equation:

  4. Calorimetry • Background • When two objects such as hot metal and cold water are brought into contact, the heat lost by the hotter object is equal to the heat gained by the cooler object. (2) qwater = - qmetal The minus sign is necessary since heat loss is an exothermic process (q is negative) while heat gain is an endothermic process (q is positive).

  5. Rearranging Eqn (3) leads to: - swater x gwater x DTwater (4) smetal = gmetal x DTmetal Calorimetry • Background • Substituting Eqn (1) into Eqn (2) leads to an equation that allows us to calculate the specific heat capacity of a metal by making a few simple temperature measurements. (3) swater x gwater x DTwater = - smetal x gmetal x DTmetal

  6. Calorimetry • Procedure • Determine the mass of your assigned metal by emptying the metal onto a paper towel and weighing the empty test tube with its stopper. Return the metal to the test tube and weigh the test tube with its stopper again. • Place the test tube in a beaker of boiling water for 10 minutes. Be careful not to allow any water to splash inside the test tube. The metal must remain dry.

  7. Calorimetry • Procedure • While the metal is heating, weigh two nested styrofoam cups (coffee cup calorimeter). • Add about 40 mL of water to the inner cup and weigh the setup again. Determine the mass of water in the calorimeter. • Measure and record the temperature of the water in the calorimeter.

  8. Calorimetry • Procedure • Remove the test tube from the boiling water and quickly empty the contents into the calorimeter. • Stir the contents of the calorimeter and record the highest temperature reached. Be sure the temperature probe is not touching the metal when you make your temperature measurements.

  9. power connector and serial/USB connector USB connector on computer temperature probe connected to the Microlab unit

  10. 2 1 graph area 3 data table live data

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