2100
Experiment Name________________________________________________________________________________
ChBE #4
Due: Fri., April 6
Please follow the reporting guidelines outlined in the syllabus. Sign the Honor Code and use this page as
a coversheet for your report.
Honor Code:
I commit to uphold the ideals of honor and integrity by refusing to betray the trust bestowed upon me
as a member of the Georgia Tech community.
_______________________________________
Signature
Heats of Solution & Reaction
Equipment per group:
Baking soda (1 box)
Vinegar (32 oz)
Measuring spoon
Aluminum foil
1 Styrofoam cup
1 Digital thermometer (+1 Battery)
1 50-ml Centrifuge tube
Note: This is a two-part experiment and your report is thus allowed to be two pages long. Any
supplementary materials (pictures, calculations, etc.) that you would like to include may be attached
in additional pages.
Part I
Instructions:
1. Fill your centrifuge tube with about 25 ml of water. Record the amount of water used as precisely
as possible.
2. Measure the temperature of the water. You might want to use the Fahrenheit scale for increased
resolution.
3. Add 1 teaspoon of baking soda to the water in the centrifuge tube.
4. Add lid and shake vigorously for 30 seconds.
5. Measure temperature of the aqueous solution.
6. Use the thermocouple to stir if you have the baking soda has not dissolved entirely.
7. Record the largest change in temperature compared to your starting temperature and the amount
of solution obtained.
Reporting:
1. How much water did you use? How much baking soda did you add?
2. How does the temperature of the water change upon addition of sodium bicarbonate?
3. Calculate the specific heat of solution of sodium bicarbonate.
4. Discuss how accurate you results are.
5. Name the source of the largest experimental error.
6. Suggest improvements of the experimental procedure to increase your accuracy.
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Part II
Part II requires you to boil a solution; if no one in your group has access to a
stove, please arrange with the TA or Instructor to boil your solution in a lab.
Note that while these instructions should work, if followed carefully, you can
troubleshoot this experiment easily using internet resources.
Instructions:
1. Add the 32 ounces of vinegar to a pot or beaker. Insert the thermometer.
2. Add around 4 tablespoons (12 teaspoons) of baking soda to the vinegar VERY SLOWLY. If you don't
add the baking soda slowly, you'll essentially get a baking soda and vinegar volcano, which will
overflow your container. Use the thermometer to monitor the temperature of the resulting
mixture and record the change in temperature that you observe when adding the baking soda to
the vinegar.
3. Boil the solution to concentrate the reaction product. You can just remove the solution from heat
once you have 100-150 ml of solution remaining, but the easiest way to get good results is to
simply boil the solution until a crystal skin or film starts to form on the surface. If you use lower
heat are you less likely to get yellow or brown liquid, but it will take longer. If discoloration occurs,
it wont hurt your results.
4. Once the skin forms on the surface, you should scoop a small amount of these crystals off of the
surface and keep them for later (using your handy plastic measuring spoon or the thermometer
probe) or you can scrape some crystals off the sides of the pot. Make sure to then stir the solution
so that the film dissolves in the warm solution (use the probe from the thermometer to stir the hot
solution, if necessary).
5. Pour the concentrated solution into your clean, empty Styrofoam cup, and immediately cover it
with aluminum foil to prevent any further evaporation. You should not have any crystals in your
solution. If you do have crystals, stir a very small amount of water or vinegar into the solution, just
sufficient to dissolve the crystals.
6. Place the covered container of your solution in the refrigerator to chill for at least 1 hour (or in the
freezer for faster chilling). Make sure that your solution is at least room temperature or cooler
before proceeding to the next step.
7. Once the solution is chilled, remove the aluminum foil from the top and spread it onto a flat
surface (make sure it is dry). Place the crystals that you recovered from the hot solution in the
center of the foil (if you couldnt recover crystals, use a small amount of baking soda, but be aware
that this will contaminate your product). You can also do the next step by pouring your solution
into a clear plastic container.
8. Pour the solution from the cup slowly onto the crystals on the aluminum foil. Observe what
happens as the solution comes into contact with the crystals. As you continue to pour the solution,
insert the thermometer probe into the growing pile. What is the temperature during this process
and why? (If using a mold or some secondary container in which you can better observe the
process, just pour your liquid into a clear plastic container and add the crystals, making sure to
insert your temperature probe before adding the crystals.)
9. If you like, you can reuse the productjust heat it again in some water or vinegar (on the stove or
in the microwave). It is safe to handle, but I wouldnt recommend eating it. It is not toxic, but this
formulation is not meant to be edible.
10. Return the assigned thermometer (with battery) and measuring spoon when you are done.
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Reporting:
1. How does the temperature of the vinegar change upon addition of sodium bicarbonate?
2. What reaction is taking place? Is this reaction endothermic or exothermic?
3. Calculate the specific heat of reaction.
4. What is the name of your product and what is it commonly used for?
5. Describe the process that you observe as you pour the solution onto the crystals. Is the process
endothermic or exothermic?
6. What is the latent heat associated with this process?
7. Is it possible to speed or slow the process? What are some possible sources of error? Explain.
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