Experiment

12

Comparison of Antacid Tablet Effectiveness

Overview

In this experiment, several brands of commercial antacid tablets were analyzed by students for their ability to neutralize stomach acid. Students were asked to write their findings on the chalkboard so that a comparison could be made as to the cost-effectiveness of the various antacids available.

Calculations

Brand of antacid ___________________________________________________________________

The following were available:
Maalox, Mylanta, Milk of Magnesia, Rolaids, Tums, CVS Brand

Active ingredient ___________________________________________________________________

This was indicated on the label. Most commonly antacids contain calcium carbonate, magnesium hydroxide, aluminum hydroxide or sodium hydrogen carbonate.

Amount of active ingredient _________________ Color of tablet solution (if any) __________________

Total volume of HCl used to dissolve tablet _______________________________________________

For most students, this would have been 50.0 mL of the 0.500 M HCl solution. If you required more than 50.0 mL, you were asked to record how much additional HCl you used.

Number of moles of HCl added to tablet (show calculation):

The Molarity of a solution represents the number of moles of solute contained in 1.00 Liter of the solution.  The HCl solution you used to dissolved the tablet, therefore, contained 0.500 moles of HCl in each liter of the solution. The molarity of a solution can be used as a conversion factor between the volume of the solution taken and the number of moles of solute present.  For 50.0 mL of 0.500 M HCl, the number of moles of HCl present is given by:

(50.0 mL) × (1.000 L/1000 mL) × (0.500 mol/1.000 L) = 0.0250 mol HCl taken

Initial volume of NaOH in the buret _______________________________________________________

Final volume of NaOH in the buret ________________________________________________________

Volume of NaOH used from the buret _____________________________________________________

Suppose the initial volume reading of NaOH in my buret was 1.21 mL, and the final volume at the color change was 41.35 mL. Then the volume of NaOH used in the titration was

(41.35 mL - 1.21 mL) = 40.14 mL

Number of moles of NaOH added from the buret (show calculation)

I used 40.14 mL of 0.500 M NaOH: the number of moles of NaOH used is therefore

(40.14 mL) × (1.000 L/1000 mL) × (0.500 mol/1.000 L) = 0.0201 mol to 3 significant figures

Number of moles of HCl not consumed by tablet (show calculation)

The number of moles of HCl not consumed by the tablet is indicated by the number of moles of NaOH required in the titration: 0.0201 mol of HCl was not consumed by the tablet.

Number of moles of HCl consumed by tablet (show calculation)

We added 0.0250 mol of HCl to the tablet, and then found that 0.0201 mol of HCl was not consumed by the tablet by titration with the NaOH. So the amount of HCl that was consumed by the tablet is

(0.0250 mol taken) - (0.0201 mol not consumed) = 0.0049 mol HCl consumed by the tablet

Mass of HCl (MM 36.5 g) consumed by tablet (show calculation)

(0.0049 mol HCl) × (36.5 g HCl/1 mol) = 0.18 g HCl

Compare results for the mass of HCl consumed per tablet.

This is just a place for you to write down the information that other students provided on the blackboard.  You should have at least 3 sets of data (your own, and the data for two different brands of antacid provided by other students).

Cost effectiveness

You are given data about the cost of each antacid, how many tablets were in each bottle, and the number of milligrams of active ingredient in each tablet.

 BRAND ANTACID # TABLETS Mg ACTIVE INGR. COST CVS 150 500 \$2.99 Magnesia Tabs 200 311 \$4.99 Maalox 35 1000 \$3.99 Rolaids 75 550 \$2.79 Mylanta 35 1000 \$3.99 Tums 75 500 \$2.99

For the calculations shown earlier, it was found that for my tablet, the tablet consumed 0.18 g of HCl. Suppose my tablet was a "CVS Brand" from the table above. The cost of one CVS tablet is

(\$2.99/bottle) × (1 bottle/150 tablets) = 0.0199 \$/tablet (about 2 cents per tablet)

the amount of HCl consumed for this cost would be

(0.18 g HCl/1 tablet) × (1 tablet/\$0.0199) = 9.0 g HCl consumed per dollar