Laboratory: Acids, Bases, and MOM!
(This
lab was adopted by Kris Young for CHE 106 from a lab previously developed by
Tod Treat and was revised by Virginia Lehmann, Parkland College.)
Report Requirement: Answer all of the questions/do all the computations
requested in italics. Questions not in italics do NOT need to be answered. You do
NOT have to write a formal lab report. You should write your answers into a word
processing program and save the file. Submit the tables to the Lab-Acids/Bases
Drop Box as .html, .pdf or .rtf formatted files. Copy and paste the answers to all
remaining questions in the appropriate space of Lab-Acids/Bases Report. LabAcids/Bases Report can be found on the Content page or under Assignments 
Quizzes.)
Labs not submitted in the appropriate area will not be graded.
Report Scoring: 20 points total. Questions valued as marked.
Working with a Partner: You are permitted to work with a partner. If you do
so, the experimental data reported may be the same, but you need to write your own
answers to each question. At the beginning of each question you should note that
you worked with a partner by writing “Lab Partner (fill in name).”
Goals:
1.
2.
3.
4.
Learn to make careful observations
Learn to make hypotheses and design an experiment to test the hypothesis
Create a pH scale using an indicator
Identify chemicals as acids or bases
Materials Needed:
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Graduated cylinder (from Lab Kit)
Pipettes or syringe (from Lab Kit)
pH paper (from Lab Kit)
clear plastic pudding cups or a number of small clear jars of some sort
knife
blender (optional)
microwave
microwave safe bowl (with lid) – should be about pint sized
spoons
white paper (optional)
Chemicals Needed:
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A purple (red) cabbage
Water
Red food coloring
Continued on next page
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Alcohol (optional)
White vinegar or lemon juice, milk, baking soda, apple juice, and Milk of
Magnesia (note: get the white, NOT colored mixture as the colors will interfere
with the lab). If you do not have these exact items, substitutions of similar
substances can be made with permission of the instructor.
From the Desk of “Dr. Dave,” M.D.
Remember my comments in the memo. Well folks, as part of the training course, here is
a very hands on activity to help you learn about acids and bases and pH. Before you can
diagnosis acidosis or alkalosis, you have to know what is acidic and what is basic and
how to test for them. So you are going to make a pH indicator and create the color chart
that indicates approximate pH level. Then you will tests some common chemicals to
check their pH.
Also, to help you bone up on neutralization reactions, you will observe how antacids
work, by neutralizing faux “gastric juices.”
And now back to my golf game…
Dr. Dave
In chemistry, it is important to be able to observe carefully and measure accurately. In
this experiment, you will make observations and measurements using several common
substances.
The Neutralizers
One of the most important groups of chemicals can be called the Neutralizers because of
their ability to neutralize each other. There are two types of neutralizers: acids and bases.
You’ve probably heard of each of these before.
Question 1: (2 points) List three things you know about the properties/characteristics of
acids and three things you know about the properties/characteristics of bases.
Lab Description:
A. Using Indicators to Identify Acids and Bases
How do you identify a substance as an acid or base? One technique is to use an indicator
-- a substance that changes color when the acidity of the solution changes. Many of these
are the colors that occur naturally in fruits, vegetables, and flowers.
1) Preparation of Red Cabbage Indicator (RCI)
A very useful indicator that we will use is made from red cabbage. Use the following
directions and make some RCI.
Take 1 red cabbage and cut it in half. Use a knife to cut that half into shreds. (Throwing it
into a blender also helps intensify the color.) Stuff the shredded cabbage into a
microwavable bowl (1 pint). Pour in enough water to nearly fill the container. Put a lid on
it and microwave for 5 min. (full power); stir; microwave
again for 5 min. (full power); stir; microwave again for 5 min.
(80 power). Pour off juice into bottle (CAUTION: HOT!)
Discard remaining cabbage or use in your favorite kraut
recipe. Store RCI in refrigerator until use! It should be a
purple to blue color, depending on the pH of your water as
RCI is purple at a pH of 7. Some suggest adding a couple of
tablespoons of alcohol to prevent bacterial growth.
If you do not want to make the RCI, you may be able to purchased prepared (jarred) red
cabbage in juice, and use the juice. Sorry about the stink, CHE 106!!!
2. Comparing Red Cabbage Indicator to Red Food Coloring
Sometimes people confuse an indicator with a solution that just happens to have a color.
Use the following procedure to compare the two red solutions using common household
substances.
a) Collect 1 small cup of vinegar or lemon juice, 1 small cup of Milk of Magnesia
(MOM), and 6 clear glasses or cups.
b) Pour a small amount of vinegar (or lemon juice) into two cups, pour a small amount of
Milk of Magnesia into two cups, and leave the last two cups empty for controls. You may
wish to place the cups on a white sheet of paper for the next step. Note: For MOM, either
pour directly from the bottle or use the teaspoon cup provided. Do not use your
graduated cylinder as it is very difficult to clean MOM out of a g.c.
c) Add about 5 drops of Red Food Coloring (RFC) into one control cup, one vinegar cup,
and one MOM cup. Make observations and prepare a table for your report like the one
shown below.
d) Now add about 20 drops of the Red Cabbage Indicator (RCI) into one control cup, one
vinegar cup, and one MOM cup. Make observations and place them into your table.
Indicator
Control
MOM
Vinegar
Red Food Coloring (RFC)
(5 drops)
Red Cabbage Indicator (RCI)
(20 drops)
Question 2: (3 points) Fill out a grid like the one above with your observations and
include it in your report. Hint – observations include things such as color, whether the
sample is clear or cloudy, whether a solid is present, etc.
Question 3: (2 points) Which is the best indicator - RFC or RCI? Why?
3. Creating a pH color chart with RCI.
There are several different kinds of acids and bases -- some are stronger and some are
weaker. How can we tell which is which? We use something called the pH Scale, which
represents the concentration of H3O+ as a number between 1 and 14 for most solutions.
pH 1
More
Acidic
2
3
5
7
9
Neutral
11
13
14
More
Basic
Notice that the scale is backwards from what you might expect: More acidic = Lower
pH. Also realize that the pH scale is like the Richter Scale for earthquakes, each step
differs by a factor of 10 (is 10 times stronger or weaker). In the Acid Base chapter of
your text, The pH Scale section is a helpful reference.
We can identify where something is on the pH scale by testing it with pH paper. The pH
scale is visible with pH paper through color changes. There are many different types of
pH paper, some which can test the entire range between 1 and 14, and others which test
narrower ranges (see photo).
We can create something similar with the cabbage indicator you made in this experiment.
Place a small amount of each of the following (or your substitutions of similar pH –you
must get permission to make a substitution) into your clear jars (use new jars!): vinegar
or lemon juice, milk, baking soda (pH ~8), apple juice, and Milk of Magnesia. Then, add
30 - 40 drops of RCI to each jar. Make observations.
Question 4: (4 points) Using the pH of the items tested as listed in the book in figure 10.4
and the RCI observations you made, fill in the chart below. Note that not every box in the
chart will be filled in as you are testing five items.
Item
Color
(with RCI)
purple
pH
7
More
Acidic
Neutral
More
Basic
4. Testing household chemicals
Now that you have a pH color chart made, you can test common household items to
determine their pH. You should choose four household chemicals that are different from
what you already used to make the chart, which are water-soluble and either clear or
white. Using clean jars, place a small amount of each in your jar and then add 30-40
drops of RCI. Make observations. Some possible household chemicals include clear
Windex, clear pop, laundry detergents, clear mouthwashes, white grape juice, salt, sugar,
and baking powder. However, do not use bleach.
Question 5a: (1.5 points) Report the color of the four new items you tested and state
whether they are an acid, base, or neutral compound based on your observations by
filling out the chart below. Please note what color your RCI is to begin with (as hard
water will give RCI a basic color and neutral compounds will not change this color).
5. Checking your work
Now that you’ve set up your RCI scale, use pH paper to test your results. Retest the four
common household items you test in part 4 with pH paper. For each item, use a spoon to
add a drop or two of the item to the pH paper. Then, compare the color of the pH paper
(where the item was added) to the chart that came with the pH paper. Record the pH
found. Make sure that you rinse and dry the spoon between uses. You may also use a
pen cap or any other implement that will deliver a drop. Again, rinse & dry between
uses. NOTE: When using pH paper, you should always bring the chemical to the paper,
and NEVER dip the paper in the chemical.
Question 5b: (1.5 points) Report the color and pH of the four items you tested and state
whether they are an acid, base, or neutral compound based on the pH, by filling out the
chart below. How do these results compare to those from part 4? If there are any
differences, please explain where they might have arisen.
Example submission for questions 5a & 5b:
My RCI color is bluish purple and it's pH is ____.
The first item tested was (name) which turns RCI to (color) and is a (acid, base or
neutral). It's pH was ______ which agrees with it being an (acid, base or neutral). [Or if
it's pH is different than the RCI indicator prediction, explain why you think it's pH is
different from the RCI color indication of acid/base/neutral.)
The second item ...
6. Application
As you likely know or have read in the "Chemistry Link to Health – Antacids”, acid-base
reactions are utilized for relieving upset (acidic) stomachs. Gastric juice is actually a
solution of hydrochloric acid, HCl. While making an HCl solution at home may be a
costly and needlessly dangerous exercise, we can still appreciate the type of reaction by
simulating this principle with the acid in vinegar (acetic acid) or lemon juice (citric acid)
and antacids. For the instructions that follow, vinegar is used.
Measure out about 10 mL of vinegar into a jar and add 30 - 40 drops of RCI. Note the
color of the solution. Then add ½ teaspoon of MOM to the jar. STIR WELL! Note the
color of the solution. Continue this process until the solution is neutral.
Question 6: (2 points) What observation signified that the solution was neutral? How
many teaspoons did it take? What does it mean when a solution is described as
"neutral"? Note: Even though teaspoon is not a metric unit, you should use the
measuring cup that came with the MOM or your own teaspoon because MOM is very
difficult to remove from the graduated cylinder. You do not need to include an estimated
digit on the number of teaspoons for this lab.
Continue to add several more ½ teaspoons and continue to note any color changes in the
solution.
Question 7: (2 points) What additional color observations have been made? What do
they mean? What happens to the patient if you give too much MOM (give a chemistry
related answer based on what you learned in this lab)?
Now we are going to reverse the reaction. Begin adding a measured amount of vinegar
back to the solution until you turn it back acidic. Note your observations.
Question 8: (2 points) How many mL of vinegar did it take to return to acidic solution?
What color was the solution at the end? Were you surprised by the amount needed?
You should write your answers into a word processing program and save the file.
Submit the tables to the Lab-Acids/Bases Drop Box as .html, .pdf or .rtf formatted
files. Go into the Lab-Acids/Bases Report and cut and paste the answers to each
question in the appropriate space. (Lab-Acids/Bases Report can be found on the
Content page or under Assignments  Quizzes.)
Labs not submitted in the appropriate area will not be graded.
This lab was adopted by Kris Young for CHE 106 from a lab previously developed by
Tod Treat and was revised by Virginia Lehmann, Parkland College. Ver. 020113