1. Purpose Background - The Power of Antacids
Lab Date:
The Power of Antacids
Purpose
To measure and compare the acid-neutralizing strengths of antacids
Background -
In this experiment, you will add an antacid to a simulated upset stomach. Not all of this acid will be neutralized, however, and so you will then determine the effectiveness of the antacid by determining the amount of acid that remains. This is done by completing the neutralization with another base, NaOH. The reaction is:
HCl + NaOH  NaCl + H2O

2. Experiment -
Pipet 25.0 mL of 0.50M HCl in an Erlenmeyer flask. This flask represents your “upset stomach.”
Add 2 or 3 drops of phenolphthalein indicator to the flask.
Crush and grind the antacid tablet with a mortar and pestle.
Carefully transfer all of the fine powder from the tablet to a weighing dish.
Measure the mass of the weighing dish with the powder.
Carefully transfer the antacid from the weighing dish to the upset stomach flask.
Now the Erlenmeyer flask represents your “relieved upset stomach”. It should be colorless.

3. Measure the mass of an empty weighing dish
Clean and prep. the buret with 0.50 M NaOH if this has not already been done.
Fill the buret to the 0-mL mark with 0.50M NaOH.
Carefully and slowly add the NaOH to the “relieved upset stomach” flask. Swirl while adding.
Add very slowly when you are near the endpoint. You should end with a light pink solution for at least one minute.
Record the final volume of NaOH remaining in the buret.
Repeat the entire procedure with another brand of antacid.

5. Analysis - Results - 1. Brand of antacid
2. Volume of HCl added to Erlenmeyer (mL)
3. Mass of weighing dish with antacid (g)
4. Mass of weighing dish empty (g)
5. Calculate the mass of antacid added to upset stomach (g)
6. Initial volume of NaOH in buret before neutralization (mL)
7. Final volume of NaOH in buret after neutralization (mL)
8. Calculate the volume of NaOH added to complete neutralization of the HCl (mL)
9. Knowing that the concentrations of NaOH and HCl were equal, calculate the volume of HCl that was neutralized by the NaOH. (mL)
10. Calculate the volume of HCl that was neutralized by the antacid (mL)
11. Calculate the volume of HCl neutralized per gram of antacid (mL/g)
Results -