Antacids Titration Lab
Teacher Preparation
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Gather all materials and place them in trays at each lab station. Have
extra flasks, beakers & graduated cylinders ready for day 2.
Prepare enough 1M HCl & 1M NaOH before & during the lab to supply
each group of 4 students with:
1M NaOH 70ml, 1M HCl 80 – 100 ml
Day 1 – Have each group practice the procedure of titrating 1 type of
antacid to become familiar with the procedure.
Coach them to start by titrating with a steady drip until pink flashes
are observed in the beaker.
Then slow down to 1 drip per 2 seconds to find the least amount
required to turn the antacid a persistent pink.
Day 2 – Titrate each antacid two times.
Each flask of neutralized antacid will have 20+ ml enough for 2
titrations.
Have them fill the buret up to the zero with 50ml 1M NaOH. This will
be enough for all 6 titrations.
Stopcocks occasionally get clogged. Ni-Chrome wire can be used to
dislodge any clogs. I’ll include some in the kit.
Stir bars end up down drains so the magnetic wand needs to be handy.
Essential Question
• Which antacid is most effective? Which
antacid will neutralize the most stomach
acid?
Data Table
Item
Starting
Volume (ml)
Ending
Volume (ml)
Observations
Materials:
• Buret, funnel, stand, clamp, magnetic
stirrer & magnet, 250ml Erlenmeyer flask,
100ml beaker, rubber stopper, 50ml
graduated cylinder, 10ml graduated
cylinder, plastic pipet, mortar & pestle,
brush, 1M NaOH, 1M HCl, phenolpthalein,
antacids: Rolaids, Maalox, Tums, or
alternatives
Antacid Neutralization
1. Clean all containers with distilled water.
2. Obtain an antacid tablet. Record the brand.
3. Grind the tablet into a powder with mortar &
pestle.
4. Transfer the powder to the 250ml Erlenmeyer
flask. Use a brush to transfer residual powder.
5. Measure precisely 40.0ml of 1M HCl in the
50ml graduated cylinder.
6. Transfer the HCl to the Erlenmeyer flask.
7. Swirl the flask to dissolve & react the antacid
tablet completely.
Titrate Excess Acid (1 of 2)
1. Make sure the stopcock valve lever is
perpendicular so it doesn’t leak.
2. Fill the buret with 1.0M NaOH above
10.0ml. Record the starting volume.
3. Measure precisely 10.0ml of antacid
solution with the 10ml graduated
cylinder.
4. Place magnet & the 10ml of antacid
solution into the 100ml beaker.
5. Add 3 drops of phenolpthalein indicator.
Titrate Excess Acid (2 of 2)
6. Place the beaker on the magnetic stirrer & turn
on the stirrer to maintain a steady spin.
7. Turn the stopcock valve lever towards parallel
to produce a steady drip.
8. When pink begins to flash in the solution slow
the drip down.
9. Use as few drips as possible to turn the
solution a steady pink.
10. Record the final volume of 1M NaOH in the
buret.
Analysis For Each Sample A (1 of 2)
1. Find the difference between the starting &
ending value of 1M NaOH used in the buret.
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Example: 11.2ml – 4.6ml = 6.6ml 1M NaOH
2. The amount of 1M NaOH used equals the
amount of excess 1M HCl un-neutralized by
the antacid.
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Example: 6.6ml 1M NaOH = XS 6.6ml 1M HCl
3. Subtract the un-neutralized 1M HCl from the
10.0ml to determine the amount of 1M HCl that
was neutralized by the antacid for every 10ml.
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Example: 10ml 1M HCl – XS 6.6ml 1M HCl = 3.4ml
out of 10ml 1M HCl neutralized by the antacid.
Analysis A
Sample
Volume of
Base Used
in Buret
Amount of
uneutralized
acid
Amount of
acid
neutralized
Analysis for Each Sample B (2 of 2)
Determine the amount of stomach acid the
antacid would neutralize.
Since you only titrated 10ml of the 40ml 1M HCl
reacted with the antacid, the antacid actually
neutralized 4x as much acid.
– Example: 3.4ml/10ml x 40ml = 13.6ml 1M HCl
The titration uses 1M HCl, however, stomach acid
has a concentration of 0.1M HCl. Multiply the
amount of 1M HCl by 10 to determine the
amount of 0.1M HCl stomach acid the antacid
would neutralize.
– Example: 13.6ml 1M HCl x 10 = 136ml 0.1M HCl
stomach acid
Analysis B
Sample
Total Amount of
Acid neutralized
by tablet
Equivalent
amount of
stomach acid