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Calorimetry

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Calorimetry General Chemistry 101/102 Laboratory Manual University of North Carolina at Wilmington Calorimetry Calorimetry Purpose To learn techniques for measuring ... – PowerPoint PPT presentation

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Title: Calorimetry


1
Calorimetry
General Chemistry 101/102Laboratory
ManualUniversity of North Carolina at Wilmington
2
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
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
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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