| In this experiment, students
will do two titrations. In part I, students
will titrate an acid with a strong base (NaOH).
They will determine what volume of base is required
for neutralizing an acid (white vinegar). Using
this data, they will be able to determine the
concentration of the acid. In part II, students
will titrate a base (laxative-milk of magnesia)
with an acid. As in part I, they determine the
amount of acid required to titrate the base
and use this volume to calculate the molarity
of milk of magnesia.
Chemicals (for part I):
1. 1M Standardized NaOH
2. Indicator-Phenolphthalein or Red cabbage
indicator
3. White Vinegar
Chemicals (for part II):
1. Tartaric Acid *
2. Indicator-Phenolphthalein
3. White Vinegar
4. Milk of Magnesia (Giant Brand)
*Note: Citric acid, oxalic acid, or ascorbic
acid can be used instead of Tartaric Acid. If
using one of these acids, make sure to adjust
the amount of weighed acid.
Equipment:
1. 50 mL Buret
2. Graduate Cylinder (10 mL, 50mL, and 250mL)
3. Stirring rod
4. Flask or a beaker
5. Balance
*Tip: Milk of Magnesia is a thick substance
that will adhere to the sides of the flask or
beaker. Be sure to use a dilute solution before
titrating, to ensure that no volume of milk
of magnesia is lost. Directions on diluting
are in the methods*
Methods (Part I): Determining the Molarity
of White
Vinegar
1. Fill the 50 mL buret with approximately
40 mL of standardized NaOH
2. Measure approximately 20-25 mL of white
vinegar and transfer this volume to a 250 mL
flask.
3. Add 3 drops of an indicator to the white
vinegar flask (either indicator mentioned above
can be used).
4. Titrate the white vinegar with (NaOH) from
the buret. Titrate until the acid has been neutralized
(a distinct color change should be visible).
5. Repeat this titration three times.
6. When the titrations have been completed,
calculate the average molarity of the white
vinegar.
Data Collection:
NaOH Buret Reading:
Initial volume: _______________
Final volume: _______________
Change in volume: _____________
Methods (Part II): Determining the Molarity
of Milk of
Magnesia
1. Weigh approximately 4.0 grams of tartaric
acid and place it in a 250 mL flask.
2. To dilute the tartaric acid, add 200 mL
of distilled water to this flask.
3. Put 2 mL of milk of magnesia into another
250 mL flask and dilute with 20 mL of distilled
water (As you add the distilled water, make
sure the rinse the sides of the flask to ensure
that all of the milk of magnesia is in solution).
4. Add 3 drops of phenolphthalein indicator
to the milk of magnesia flask.
5. Titrate with tartaric acid into the milk
of magnesia flask, until a clear solution color
is observed.
6. Perform 3 titrations and calculate the average
molarity of the milk of magnesia.
Data Collection:
Volume of Tartaric Acid used to neutralize
the milk of magnesia: ________
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