This experiment consists of
two parts. In the first portion of the experiment,
the students will be standardizing the base.
In the second part of the experiment, the students
will use the base, which was previously standardized
to titrate vinegar, which contains acetic acid.
The percentage of acetic acid in the vinegar
sample will then be determined.
* Two 50 mL burettes
* Three 250 mL Erlenmeyer flasks
* 10, 50 and 250 mL graduated cylinders
* Storage container
* Stirring rod
* Tartaric acid
* Milk of magnesia
* White vinegar
* Phenolphthalein indicator
* Distilled water
PART I: Standardization of Milk of Magnesia
Prepare a solution of milk of magnesia by
diluting 7 mL to 140 mL using distilled water.
Place 20 mL of this milk of magnesia solution
into a 250 Erlenmeyer flask and add 3 drops
of phenolphthalein indicator to the flask.
Weigh out 1.3 g of tartaric acid * and place
it into a volumetric flask and then dilute to
200 mL with distilled water. Fill a 50 mL burette
with this tartaric acid solution. Titrate the
20 mL milk of magnesia sample with the tartaric
acid solution to the end point. Tartaric acid
will give a sharp endpoint that is very distinct
and clear to recognize.
After completing three titrations of milk
of magnesia samples, calculate the average molarity
of the milk of magnesia solution.
* The tartaric acid may be substituted with
citric acid, oxalic acid or ascorbic acid.
PART II: Determination of Acetic Acid Content
in a Vinegar Sample
Take 10 mL of a vinegar sample and dilute
to 200 mL with distilled water. Fill a clean
50 mL burette with this solution. Fill a second
burette with the milk of magnesia solution that
was prepared in Part I of this experiment. Dispense
20 mL of the milk of magnesia solution into
a 250 mL Erlenmeyer flask and add 3 drops of
phenolphthalein indicator. Titrate the milk
of magnesia sample with the vinegar.
After completing three titrations of the milk
of magnesia sample, calculate the average molarity
of the vinegar and then determined the percentage
of acetic acid in the vinegar sample when it
is given that the density of the vinegar solution
is 1.00 g/mL.