Titrating Household Vinegar
Objective: Using a known concentration of a base (NaOH),
Determine the molar concentration of acetic acid in vinegar (CH3COOH)
Safety: Sodium Hydroxide is caustic and will burn skin and eyes.
PreLab:
answer in complete sentences in context
1. Write a balanced equation for a reaction between sodium hydroxide and acetic acid.
2. What is the purpose of doing a titration?
3. What is the purpose of an indicator?
4. What color does phenolphthalein turn and at what pH?
5. How many times should you do a titration to be sure of your results and limit your error?
6. What are the products at the end of this titration?
7. What is the concentration or [H+] and [OH-] like at the endpoint of this titration?
Trial 1
Trial 2
Trial 3
Data: Final buret reading (-)
mL
mL
mL
Initial buret reading =
mL
mL
mL
Volume of base added
mL
mL
mL
M
M
M
mL
mL
mL
Molarity of base
Volume of vinegar
8. Calculate the Molarity for each titration. Show all work with units. Round final answer only.
MAcid x V Acid = M base x V Base
Titration 1
Titration 2
Titration 3
9. Calcuate the average Molairty (add together all three trial results and divide by 3)
10. Vinegar is required by the government to be between 5% and 7% acetic acid or 0.840 Molar.
Using your average molarity, calculate the % error: accepted—actual x 100 = %
Accepted
Conclusion: 1. Objective
2. Claim, Evidence , reasoning Summar ize your test r esults with the pr oof and r eason
as to why
Identify sources of error as you explain your % error.
Titrating Household Vinegar
Objective: Using a known concentr ation of a base (NaOH),
Determine the molar concentration of acetic acid in vinegar (CH3COOH)
Safety: Sodium Hydr oxide is caustic and will bur n skin and eyes.
Materials: 250mL Er lenmeyer flask. 50.0 mL Bur et , 1 small beaker for waste, 10 mL gr ad cylinder ,
Phenolphthalein, 0.500 molar NaOH , CH3COOH, ring stand with Buret clamp, plastic funnel, distilled water.

A buret allows you to accurately measure the amount of liquid you add to a container.

The first point to notice about your buret is that the numbering is “upside-down” compared to
other measuring devices you have used. Burets measure the amount of liquid delivered from
them, not the amount they contain. A full buret will read “0 mL” and an empty 50 mL buret will
read “50 mL.” You read the level in the buret from the bottom of the meniscus, as you do with
a graduated cylinder.


0
10
Before you start to pour anything into the buret, check that the stopcock of the buret is closed.
(Closed is horizontal. Open is vertical. If you try to fill a buret with the stopcock in the vertical
position, you’re likely to get your shoes wet.)
20
30
Before using the buret you should rinse it with distilled water and then with a small amount of
your titrant (NaOH)
40
50

To fill the buret, use a funnel. Put a waste beaker under the buret while you fill it, to catch any
spills.

If you notice that your buret is dribbling liquid even when the stopcock is in the closed position,
the stopcock may be assembled incorrectly. Consult the instructor for help.

Open the stopcock and allow a small amount of 0.50 M NaOH to run through the tip of the
buret. This should clear out the bubbles… Then read the amount of NaOH in your buret and
record. Be sure to estimate to the 0.01mL
stopcock
Procedure: Read the above information before starting
A. Set up your equipment and obtain all supplies from your station.
B. Measure 10.0 mL of vinegar in a graduated cylinder and put into a 250 mL Erlenmeyer flask and set aside.
C. Rinse your buret with DeIonized water from your wash bottle. Let the water run through into your waste container.
D. Put a small amount of 0.50 M NaOH into your buret ( about 2 mL) to coat the inside of the buret . Drain out the
excess NaOH into your waste container.
E. Fill your buret with 0.50 molar NaOH, as outlined above, to just above the 0.0 mark.
F. Open the stopcock and release a small amount of NaOH into your waste container.
G. Read and record the Initial Buret reading. Be sure to read the bottom of the meniscus. * remember to estimate
your final number.
H. Place 1 or 2 drops of phenolphthalein indicator into your 250 mL flask of vinegar.
I. Place the flask under the buret. Open the stopcock and allow about 7-10 mL of NaOH run into the flask as you swirl
and keep track of the color, how long it lasts and how fast the color disappears.
J. As you near the endpoint the color will remain longer. You will eventually dispense the NaOH, drop by drop, until
the very pale pink color appears and stays.
K. Record your Final Buret reading.
L. Pour the contents of the flask down the drain. Rinse out the flask first with tap water then with DI water. Complete Trial 2 and 3. Be sure you have enough NaOH in your buret before you start your titration. Check your first
titration to see about how much you need.
Clean up according to teachers instructions.