Experiment 28
March 23, 2010
Dr. Scott Buzby, Ph.D.
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To measure, using a calorimeter, the energy
changes accompanying neutralization reactions
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Learn the Kelvin temperature scale
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Define heat capacity
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The kelvin (K) is a unit increment of
temperature and is one of the seven SI base
units (meter, kilogram, second, mole, ampere &
candela)
The Kelvin scale is a thermodynamic (absolute)
temperature scale referenced to absolute zero,
the theoretical absence of all thermal energy
By definition it is zero kelvins (0 K)
1 Kelvin = 1° Celsius
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Every chemical reaction is accompanied by a
change in energy, usually in the form of heat
The energy change of a reaction is called the
Heat of Reaction or the Enthalpy Change (DH)
If heat is evolved, the reaction is exothermic
and DH < 0
If heat is absorbed, the reaction is endothermic
and DH > 0
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Tonight we will measure the heat of
neutralization when an acid and a base react to
form water
This is measured by allowing the reaction to
take place in a thermally insulated vessel called
a calorimeter
The heat given off by the reaction will cause an
increase in the temperature of the solution and
the calorimeter
If the calorimeter was perfect, no heat would be
by the calorimeter or the laboratory
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In order to determine the heat of reaction we must
first determine the amount of heat absorbed and
the heat capacity of the calorimeter
Heat capacity of the calorimeter is the amount of
heat (in joules) needed to raise its temperature by 1
kelvin
The heat capacity of a calorimeter is determined by
measuring the temperature change that occurs
when a known amount of hot water is added to a
known amount of cold water
The heat lost by the hot water is equal to the heat
gained by the cold water and the calorimeter
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Procedure on top of Page 322
Graph Temperature vs. Time for hot and cold
water
Do the calculations on the report sheet
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Page 320-321 and example 28.1 for help
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Procedure:
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Part B – Page 322
Part C – Page 323
Graph Temperature vs. Time for solution
Do the calculations on the report sheet
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Page 320-321 and example 28.2 for help
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Report Sheet – Pages 325-327
Questions – Page 327
Three Graphs – Pages 328-330 or print-outs
Pre-Lab Experiment 33 – Page 427
Reminder – Course evaluations will be next
week