Dissolving and Reaction of Alka-Seltzer
PURPOSE
Determine how temperature affects
the rate at which Alka-Seltzer dissolves.
PERFORMING THE EXPERIMENT
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Use hot and/or cold water from
the faucet or already on the table to adjust the temperature of water to
whatever temperature you desire (as measured on the Celsius scale on the
thermometer provided). Obtain data over a large range of temperatures
rather than using temperatures clustered around room temperature.
(NOTE: Somebody should use the hottest water available, and somebody
the coldest.)
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Add water to the plastic beaker
until the water reaches the 100-milliliter mark. Obtain one Alka-Seltzer
tablet, if necessary, by carefully tearing open a new package which contains
two Alka-Seltzer tablets. Check your temperature once again.
Then note the exact time at which you carefully drop one Alka-Seltzer tablet
into the beaker. Do not stir or swirl the solution; simply let the
Alka-Seltzer tablet react on its own so that each person uses identical
reaction conditions. You and your adult partner should keep careful
track of the time it takes for the Alka-Seltzer tablet to dissolve completely
(when you can no longer see any white solid in the beaker). Be patient!
-
Check the temperature again
at the end of the reaction, and determine an average temperature from the
one at the beginning and the one at the end of the time.
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Pour the contents of the beaker
down a sink drain or into a can on the table.
-
Rinse the beaker, and return
it to the table.
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On the data sheet nearby, write
your first and last name neatly, your average temperature, and the time
required for complete reaction (in seconds).
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Plot your results clearly on
the graph paper provided by reading up the vertical axis until you come
to your time, reading across the graph horizontally until you come to your
temperature, and then placing a small circle. Note that your circle
will not be on either axis! Do you observe any trend based on data
plotted so far?
QUESTION TO THINK ABOUT
1. Are reactions
in our body speeded up or slowed down when we have a fever?
EXPLANATION
The primary active ingredients
in Alka-Seltzer according to its label are aspirin, sodium acetylsalicylate
(an analgesic, a medication that reduces or eliminates pain), sodium citrate
(an antacid, a substance that neutralizes acids), as well as sodium bicarbonate
and citric acid. The latter two substances do not react when kept
dry in the tablet form, but do react in water solution to produce the fizz
of bubbling carbon dioxide gas according to the following reaction.
sodium bicarbonate
+ citric acid ---> carbon dioxide (gas)
+ water + sodium citrate
Like most chemical reactions,
the speed of this reaction increases at higher temperatures and decreases
at lower temperatures.
EQUIPMENT NEEDED
250-mL plastic beakers; alcohol
thermometers; Alka-Seltzer tablets; water.
DISSOLVING AND REACTION
OF ALKA-SELTZER GRAPH
REFERENCE
-
See the website
www.alka-seltzerplus.com/as/experiment/student_experiment.htm.
Click on Experiment 1. You may also want to try Experiments 2 and 5.
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