Enthalpy Lab
Background Every reaction either aborbs heat from its environment (endothermic) or releases heat
into its environment (exothermic). The amount of heat transferrred depends on the
amount of the limiting reagent in the reaction. Therefore, there should be twice as much
heat transferred when the amount of the limiting reagent is doubled.
Common reactions that can used in solution include: (1) single replacement reactions
where a metal is placed in an acid (Mg + HCl); (2) double replacement including
neutralizations (NaOH + HCl); and (3) heat of solution reactions where a soluble solid in
placed in water (NH NO + H O).
4 3 2
Purpose To use a Temperature Sensor to investigate the enthalpy of a reaction.
To determine the molar enthalpy of a reaction for various amounts of limiting reagent.
Equipment PASPORT Xplorer GLX stainless steel temperature probe
digital balance, 200 Ä… 0.01g graduated cylinder, 100 Ä… 1 ml
utility clamp base and support rod spatula
weighing papers styrofoam cup or calorimeter stirring rod
Chemicals specify your chemicals
Safety Follow all directions for using the equipment.
Wear safety glasses, gloves, goggles and protective clothing.
Handle and dispose of all chemicals and solutions properly.
Procedure
Equipment
Place the small aluminum cup inside its collar and place inside the larger container
(calorimeter).
Insert the stainless steel temperature probe into the stopper and place in calorimeter
cover.
Adjust the temperature probe so that its tip is close but not touching the bottom of the
inner cup.
Insert the stirring rod through the small opening in the calorimeter cover.
Determine the desired volume. Fill the inner cup with tap water then transfer the water to
a graduated cylinder to determine a safe volume of reaction mixture that can be used.
This desired volume and should remain constant for all trials.
Turn on Xplorer GLX and plug the temperature probe into or on the left side of
the GLX.
Open the Graph Display.
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Record Data Reaction Type A: Solid into Liquid
Tare the balance to the weight of the weighing paper.
Weigh out about convenient amount of the solid chemical. Start with small amounts
(about 0.1 moles)
Measure the desired volume of water/acid using a graduated cylinder and place in the
inner cup of the calorimeter.
Press to begin recording the temperature of the water in the inner cup.
Once the temperature remains reasonably constant, carefully add the solid chemical to
the cup.
Observe the change in temperature on the Graph display.
Observe the temperature for at least one minute after the maximum temperature was
reached.
Press again to end data recording.
Remove the Temperature Sensor from the cup and rinse and dry the sensor.
Dispose of the solution as directed. Rinse and dry the cup.
Repeat the above steps three additional times using different amounts of the solid
chemical.
The final temperature should never exceed 75°C.
Reaction Type B: Liquid (Solution) into Liquid (Solution)
Measure a set volume of the excess reagent in a graduated cylinder and carefully pour it
into the inner cup.
Measure a set volume of the other reagent into a graduated cylinder so that the sum of
the two volumes is the desired total volume.
Press to begin recording the temperature of the excess reagent in the inner cup.
Once the temperature remains reasonably constant, add the other reagent solution to the
cup
Observe the change in temperature on the Graph display.
Observe the temperature for at least one minute after the maximum temperature was
reached.
Press again to end data recording.
Remove the Temperature Sensor from the cup and rinse and dry the sensor.
Dispose of the solution as directed. Rinse and dry the cup.
Repeat the above steps three additional times using different volumes of each reactant,
while maintaining a total volume of 100.0 mL.
The final temperature should never exceed 75°C.
Record all relevant data, process the data and present it in a meaningful, logical, and easily understood
format with attention to uncertainties.
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