Titration of Vinegar
EXPERIMENT
Titration of Vinegar
12
Prepared by Edward L. Brown, Lee University and
Verrill M. Norwood, Cleveland State Community College
OBJECTIVE
The student will become familiar with the techniques of titration and
expressing a solution’s concentration as molarity and mass percent. In
this experiment, you will use the NaOH solution that you standardized in
Experiment 11 to determine the concentration of vinegar in units of
molarity and mass percent.
A
APPARATUS
AND
CHEMICALS
P P A R A T U S
Buret / Buret Clamp
Erlenmeyer Flask (250 mL)
Ring Stand
Volumetric Flask (100 mL)
Volumetric pipet (25 mL)
Stir Plate / stir bar
C
Vinegar
H E M I C A L S
Phenolphthalein
Vinegar is a dilute solution of acetic acid (HC2H3O2) which is one of the many weak
acids used in chemistry. In contrast, there are only seven common strong acids: HCl,
HBr, HI, HNO3, H2SO4, HClO3, and HClO4. The difference between a strong acid and a
weak acid is the degree of dissociation when placed in water. A strong acid is essentially
100% dissociated into H+ (or H3O+) and an anion when placed in water; a weak acid is
less than 100% dissociated. Whether an acid is strong or weak does not affect its reaction
with a base - strong and weak acids both react swiftly and completely with a base.
The concentration seen on a vinegar label is typically expressed as a mass percent (mass
of solute / mass of solution × 100). The molarity of vinegar can be converted to mass
percent once the density of the vinegar solution is known. The molarity of the vinegar
provides the number of moles of acetic acid in 1 L vinegar – the moles of acetic acid can
be converted to grams acetic acid (solute) while the 1 L vinegar (solution) can be
converted into grams of vinegar (solution). Substitution, as shown in the following
example, will provide the mass percent of acetic acid in a solution of vinegar.
CHEM 1010 - Experiment 12
12-1
Titration of Vinegar
Example 1: A sample of vinegar (25.0 mL) was placed in a 100-mL volumetric flask
and distilled water was added to the line scored on the flask. The volumetric flask was
capped and shaken before 25.0 mL of diluted vinegar was withdrawn and placed in a
250-mL Erlenmeyer flask. Approximately 50 mL of distilled water was added to the
Erlenmeyer flask along with 3 drops of phenolphthalein indicator. A buret was filled
with an NaOH solution that was previously standardized (0.0987 M). A light pink
endpoint was reached after 28.4 mL of the NaOH solution was added to the Erlenmeyer
flask containing the diluted vinegar.

What is the Molarity of the diluted vinegar solution?
28.4 mL NaOH solution ×
M=
= 0.112
1× 10-3 L NaOH solution 0.0987 moles NaOH solution 1 mole diluted Vinegar solution
×
×
1 mL NaOH solution
1 L NaOH solution
1 mole NaOH solution
1× 10-3 L diluted Vinegar
25.0 mL diluted Vinegar ×
1 mL diluted Vinegar
moles diluted Vinegar
= 0.112 M
L diluted Vinegar solution

What is the Molarity of the vinegar solution?
Recall that we added 25.0 mL of vinegar to a 100 mL volumetric flask and then diluted
the vinegar with ~ 75 mL water. So, if this diluted vinegar solution has a concentration
of 0.112 M, then the undiluted vinegar’s concentration must be 4 × 0.112M, or 0.448M.

What is the Mass Percent of a 0.448 M Acetic Acid (Vinegar) solution if the density
is 1.10 g/mL?
First, “break apart” the 0.448 M into 0.448 moles solute and 1 L solution. Then, convert
0.448 moles into grams using 60.05 g/mole as the molar mass of acetic acid. This gives
26.9 grams acetic acid. Next, convert 1 L to 1000 mL and multiply by the density (1.10
g/mL) to find the mass of the solution (1100 g solution). Finally, the mass percent is
calculated as follows:
26.9 g HOAc
× 100 = 2.45 %
1100 g Solution
CHEM 1010 - Experiment 12
12-2
Titration of Vinegar
Density of Vinegar
Procedure
1. Obtain a dry 100 mL volumetric flask from your instructor and determine its mass to
the nearest 0.001 g [Data Sheet Q1].
2. Using a suction bulb and a 25 mL pipette, place 25.00 mL of vinegar into the
volumetric flask.
3. Determine the mass of the flask and vinegar to the nearest 0.001g [Data Sheet Q2].
4. Dilute the 25.00 mL of vinegar in the 100 mL volumetric flask with distilled water
until the final volume is 100.00 mL (add distilled water to the scored mark on the
volumetric flask).
5. Stopper and mix this solution by inverting it several times.
6. Using a suction bulb and a different 25.00 mL pipette, remove 25.00 mL of the
“dilute” vinegar and place it in a 250 ml Erlenmeyer flask (FLASK 1).
7. Remove an additional 25.00 mL of the “dilute” vinegar and place it in another 250
ml Erlenmeyer flask (FLASK 2).
8. Remove an additional 25.00 mL of the “dilute” vinegar and place it in another 250
ml Erlenmeyer flask (FLASK 3).
9. Add ~ 75 mL distilled water and 3 drops phenolphthalein to each flask.
10. Add a stirring bar to Flask 1. Use the same stirring bar for Flasks 2 and 3.
Titration of Vinegar
11. Obtain the sodium hydroxide (NaOH) solution (~ 0.1 M) that you standardized last
week from your Instructor.
12. Obtain a clean buret and a buret clamp. Make sure the stopcock on the buret is
closed.
13. Add ~ 5 mL of the NaOH solution to the buret (rotate the buret to wash down the
sides with this NaOH solution) and empty it into the sink. Repeat with another 5
mL of the NaOH solution.
14. Then, fill the buret to the top with the NaOH solution. Place a small beaker or plastic
cup under the stopcock and fully open the stopcock allowing ~1 mL of base to exit.
Repeat opening and closing the stopcock until no more air bubbles exit the tip of the
buret.
15. Adjust the buret so that it is directly above the flask and the stirring plate.
16. Record the starting volume of NaOH in the buret [Data Sheet Q3] and begin to
slowly add the base to Flask 1.
17. As base drops onto the acid solution, a pink color appears that rapidly disappears
with stirring. As time passes, the color remains longer – you should add the base
CHEM 1010 - Experiment 12
12-3
Titration of Vinegar
dropwise at this point. Eventually, a single drop of base will change the colorless
solution to a persistent (for at least 30 seconds) light pink.
18. Record the final volume of base used [Data Sheet Q4].
19. Repeat Steps 16 – 18 for Flasks 2 & 3.
Dispose of all solutions in the sink – flush with plenty of water.
Return Clean Burets To Your Instructor. Return any remaining 0.1M NaOH to
your Instructor.
Waste Disposal:
Lab Report:
Once you have turned in your Instructor Data Sheet, lab attendance will
be entered and you will be permitted to access the online data / calculation submission
part of the lab report (click on Lab 12 – Titration of Vinegar). Enter your data
accurately to avoid penalty. The lab program will take you in order to each calculation.
If there is an error, you will be given additional submissions (the number and penalty to
be determined by your instructor) to correct your calculation.
CHEM 1010 - Experiment 12
12-4
CHEM 1010 - Lab 12
Student Data Sheet
Density of Vinegar
1. Mass of 100 mL Volumetric Flask
g
2. Mass of Volumetric Flask + Vinegar
g
Titration of Vinegar
Trial 1
Initial buret reading
0
Final buret reading
Trial 2
mL
0
mL
Trial 3
mL
0
mL
mL
mL

Names:
CHEM 1001 - Lab 12
Instructor Data Sheet
Density of Vinegar
1. Mass of 100 mL Volumetric Flask
g
2. Mass of Volumetric Flask + Vinegar
g
Titration of Vinegar
Trial 1
3. Initial buret reading
4. Final buret reading
CHEM 1010 - Experiment 12
0
Trial 2
mL
mL
0
Trial 3
mL
0
mL
mL
mL
12-5