Eggshell/Antacid Burets Lab
Introduction/Purpose:
The purpose of this lab was to determine the percent composition, the percent of the total
mass of the compound. First, the antacid tablets were put into a bag and were smashed, then weighed
and the fine powder went into each of the three flasks. When each sample was reacted with the
hydrochloric acid, the qualitative data was that it fizzed. It was known when the reaction was done
because there was no fizzing present. Water was then washed on the sides of the flask. This was
important because all of the reactant needed to be in the flask. The phenolphthalein was then dropped
into each of the flasks, this was added for the titration- causing it to turn pink. The purpose of why this
lab was performed would be to visualize the titrations.
Materials:

Crushed antacid tablets(tums)/eggshells
* Hydrochloric Acid

Sodium Hydroxide
* Calcium Carbonate

Hammer
* Plastic bags

Burets
* Clamp

Stopcock
* Stand

Triple Beam Balance
*Notes/Packet/Paper/Pencil

Phenolphthalein indicator solution
*Erlrnmeyer flasks
Procedure:
1.) First, put some tums (antacid tablets) in a bag.
2.) Next, smash them with a hammer.
3.) Then, weigh (3) ½ gram samples into different flasks.
4.) React each of the flasks with 25.0 mL of the 1.0 M of the hydrochloric acid.
5.) Wash all the sides of the flask with some water. (to make sure all of it is in there.)
6.) Add a few drops (2-3) of the phenolphthalein to all of the flasks.
7.) Make a titration with the sodium hydroxide.
Data:
Mass of crushed
antacid tablet
Volume of HCL used
Initial reading, NaOH
Buret
Final Reading, NaOH
buret
Volume NaOH
Moles of HCl
consumed by antacid
Mass of NaCO3 in
sample
% NaCO3 in sample
Trial 1
½ gram
Trial 2
½ gram
Trial 3
½ gram
24.5 M
0
50
25 M
0
35
25.3 M
0
20
1.0 M
24.5 mL
1.0 M
25 mL
1.0 M
25.3 mL
-1.28
-0.5
0.27
-2.55%
-1%
0.53%
*See separate sheet for sample calculations, qualitative data, and reactions.
Analysis and Conclusion:
In conclusion, there were neutralizations because the acid and base balanced out in the
end. The HCL in the lab acted as the acid because it donated a hydrogen in the reaction. The
HCL reacting with the CaCO3 was a decomposition reaction and double replacement because
the oxygen lost one and went to the water. The oxygen in CaCO3 acted as the base because it
accepts the hydrogen. The reaction was over when the fizzing had stopped (carbon dioxide was
being released.), qualitative data. Another piece of qualitative data is that the liquid turned pink
when the phenolphthalein, an indicator, was added to the solution. The NaOH was used to see
what was left over. Some quantitative data: ½ gram was used for the crushed antacid tablets, the
initial reading for each trial was 0, the final readings were between 20 and 50, and moles of HCl
consumed by antacid were between 24.5 and 25.3. (More are in notes.)
Burets are pieces of glass used to deliver amounts of liquid, usually for titrations. It’s a long,
glass cylinder that has one opening at the top and is closed at the bottom by a stopcock valve.
This controls the flow of the liquid.
Questions answered: When reading the buret, the numbers are read from the top down. When
recording buret volume, the decimal point should be recorded to the hundredth place. The sides
of the buret are tapped after filling it to make sure all the solution was delivered. A few
milliliters are drained through the tip after filling the buret because the hanging drop is part of
the volume being delivered by the buret. After delivering a certain volume into a flask, a drop of
liquid is hanging from the tip. This is part of the delivered volume and should be added to the
flask.
Error Analysis:
When doing this lab there were a few sources of error. While pouring the HCL into the
burets, it was spilled, running down into the beaker. This was a source error because it caused it
to over titrate. Also, when the liquid was already in the burets, some leaked out into the beaker.
That was an error because we could not measure how much was let into the beaker. The last
source error was when there was an over titration and the flask turned too pink. Some other
source errors that could have been possible would have been if water was left in the burets, or if
the sodium hydroxide sat out for too long with the lid off- sucks water out of the air. You can fix
some of them by making sure the stopcock is closed when you need it to be, try not to let as
much liquid out, try hard not to spill anything, and to make sure to keep the lid on the liquid
when you’re not using it.
Works Cited:
Mrs. Cleaver, Packet, 5/2/03
R.G. Drage Career Technical Center, Massillon, Oh.