Name:
Date:
SNC2D
Expectation C1, C2:
HOW EFFECTIVE IS YOUR ANTACID?
Purpose: to compare over the counter antacids in their effectiveness at neutralizing stomach acid, HCl
Pre-lab:
1. Details for the antacid products are shown below.
Brand
Tums
Tablets per Dose
2 tablets/dose
Costs
150 tablets for $4.79
Active Ingredients
1000 mg CaCO3 per dose
Rolaids
1 tablet /dose
150 tablets for $4.79
550 mg CaCO3 plus 110 mg
Mg(OH)2 per dose
2. The pH indicator used in this lab, methyl orange, will turn from orange when the solution is
basic, to clear when the solution reaches pH 7 (neutral) and pink when acidic. What is the
significance of pH7 in terms of hydroxide and hydrogen ions?
3. You will simulate the neutralization of stomach acid by using 1M HCl, which is similar to the
concentration in your stomach. Write balanced chemical equations for the reactions you expect
for either of the antacids examined. Refer to the special reaction of an acid and a carbonate
from yesterday’s notes *BURP*


4. Suppose you had two acids, one with a pH of 4 and another with a pH of 3. In terms of the
number of H+, which acid is stronger and by how much?
SAFETY: Strong acid is corrosive to skin and eyes.
 SAFETY GOGGLES MUST BE WORN AT ALL TIMES.
 LONG HAIR MUST BE TIED BACK, NO HATS OR LOOSE CLOTHING ITEMS.
Materials:
Safety Goggles
250 mL Erlenmeyer flask
Scoopula
Mortar and pestle
Weighing cup
Dropper
Scale
25 mL Graduated cylinder
Methyl Orange indicator
Sheet of white paper
1 molar HCl
One dose of an antacid sample (to be given to your group)
Method:
1. Crush the antacid sample using the mortar and pestle.
2. Measure the mass of the sample by taring (zeroing) the scale with the empty weighing cup and
then measuring the sample weight. The scoopula can be used to help empty the sample from
the mortar to the weighing cup. Record the mass in the Observation Table.
3. Transfer the antacid powder into the flask. Put a white paper under the flask for better
observation of the colour change.
4. Use the graduated cylinder to measure 10 mL of HCl. Add to the flask and swirl gently to
dissolve the antacid. REMEMBER, if you get hydrochloric acid on you skin or clothing, wash
with plenty of water. Clean spills with paper towels and water.
5. Add 3 drops of indicator to the flask. HOLD THE DROPPER STRAIGHT UP AND DOWN,
NOT AT AN ANGLE. This lets gravity take the drop off the dropper, and makes each drop the
same volume. Gently swirl the solution to mix.
6. Using the dropper, you will count the number of drops of HCl needed to just change the
solution from orange to clear. Begin by adding drops 5 at a time and mix well to be sure any
colour change does not disappear. Once a colour change upon addition of acid does begin, start
adding drops one at a time, and mix well between additions. Record the total number of drops.
7. Convert the drop volume to mL using the conversion factor 20 drops = 1mL.
8. Get the observation data from another group for the antacid you did not examine. Record this
data. You will be analyzing data for both antacids.
9. CLEAN UP: Dispose of contents down the sink with plenty of water. Wash equipment with
soap and water using brush. Rinse and leave in tray or hang to dry. WASH YOUR HANDS.
OBSERVATIONS
Name of Antacid
Your sample:
Other Antacid:
Other Group’s Names:
Mass of
Antacid
dose (g)
Number
of drops
of HCl
Drop volume
20 drops = 1
mL
(mL)
Total volume of HCl
neutralized (mL)
[10 mL + drop volume]
Analysis:
Record your calculated values in the table provided.
1. For each product, calculate its effectiveness by weight of antacid. (calculation: total volume
HCl used divided by the mass of the antacid sample)
2. For each product, calculate the effectiveness per dose of antacid (total volume HCl per dose)
3. Use the cost data on page 1 to calculate the cost of a single dose of each product.
Name of Antacid
Effectiveness
by weight
(mL HCl / g antacid)
Effectiveness
per dose
(mL HCl / dose)
Cost per dose
($/dose)
4. Suggest at least two sources of error for the accuracy of this investigation as carried out.


5. Which is the least expensive antacid per dose? Is it also the least effective? Support your
answer in some way using your data.