In this video, we will be covering important tips when investigating the
acidity of beverages. This experiment is Lab 4 from Vernier Chemistry
Investigations for use with AP Chemistry lab book, and correlates the Lab 4 from
the College Board's lab manual for AP Chemistry. If you're looking for a video
demonstrating acid-base titrations, visit our Video Training Library available under
the Training tab on our website. This investigation builds on the understanding
of an acid-base titration learned in first-year chemistry courses. The goal of
this investigation is to determine the concentration of an acid in the beverage
that may be a sports beverage, fruit juice or soft drink. You may also be able to
identify the acid. There are some additional challenges that need to be
considered when titrating beverages. Here are some points to consider: soft drinks
and fruit juices can contain more than one acid. Consider how this will affect the
titration when determining the acid concentration. In addition to the acid in
soft drinks, carbonation due to carbonic acid can affect the acid concentration.
Think about how to account for the carbonation. Is the acid in the beverage a
monoprotic, diprotic, or triprotic acid? Will this affect the calculation of the
acid concentration? Will any ingredients in the beverages such as food dyes affect
the titration data? For the equipment, here are two options for setting up the
titration. Either option can be used with the computer running LOGGER PRO software
or with LabQuest. This setup here uses your burette and a pH Sensor. The volume
will be manually entered for each pH reading.
The setup here uses a Vernier Drop Counter and pH Sensor. The Drop Counter will
automatically record the volume at each pH reading. If the investigation includes
identifying the acid in the beverage, calibrating the pH Sensor along with
calibrating burette or Drop Counter are important. Instructions for calibrating
the pH Sensor are in the user guide, and available in our Tech Info Library. The
default calibration for the Drop Counter is 28 drops per milliliter, and
instructions for calibrating the Drop Counter are available in the user manual,
and will be briefly described. The first step is to access the calibration option
for the Drop Counter in your data collection program. In Logger Pro, choose
Experiment, then choose Calibrate, and choose Drop Counter, and follow the
instructions on the screen. Then if you want to calibrate in LabQuest, tap on
Sensors, choose Calibrate, and choose Drop Counter. The rate when you are calibrating
should be no faster than approximately one drop for every two seconds into the
graduated cylinder. So I've readjusted the setup here now to calibrate the Drop
Counter using a 10 milliliter graduated cylinder, and making sure, again, the drop
rate is no faster than approximately one drop for everyone one to two seconds. The
intent is to collect approximately 9 to 10 milliliters of liquid in the graduated
cylinder, and the software calculates the drops per mil based on the number of drops
counted, and the manually entered volume. The calibration corresponds to the reagent
reservoir.
Be sure to use the same reagent reservoir for the calibration and for the
investigation. Once the investigation is completed, this graph representative of an
acid-base titration. The sample data was collected using Gatorade. If you're
looking for a video demonstrating the techniques and steps of an acid-base
titration, visit our website, and check out the Video Training Library under the
Training tab. For more information about our lab book, Vernier Chemistry
Investigations for use with AP Chemistry, visit our website.