Exp1 - CO2 from antacid

Exp1 - CO2 from antacid - CARBON DIOXIDE FROM AN ANTACID...

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1 CARBON DIOXIDE FROM AN ANTACID TABLET Experiment 1 INTRODUCTION Several brands of antacids contain calcium carbonate as their active ingredient. Inert materials such as binders, coloring, and flavorings are also present. In this experiment you will determine the weight percent of calcium carbonate in an unknown antacid tablet. Calcium carbonate reacts with acid and produces carbon dioxide. CaCO 3 (s) + 2 HCl (aq) Ca 2+ (aq) + 2 Cl (aq) + H 2 O (l) + CO 2(g) (1) or CO 3 2 (aq) + 2 H + (aq) H 2 O (l) + CO 2(g) (2) By reacting the antacid with excess acid and then collecting the carbon dioxide produced in a constant predetermined volume, we will be able to use the Ideal Gas Law (PV=nRT) and the molecular weight of calcium carbonate to determine the weight percent of calcium carbonate in an antacid tablet. The pressure will be monitored with a pressure sensor and temperature will be monitored using a Temperature probe, both connected to a computer via an interface unit. APPARATUS AND CHEMICALS Apparatus 3 125 mL erlenmeyer flasks 3 small vials 1 spatula 1 weighing plate 1 tweezers 1 Three Holed Rubber Stopper, set with a 2-way valve, a Temperature probe and a Pressure sensor Chemicals ~2.5 g CaCO 3 (99.9%) 1 antacid tablet ethanol HCl (4.5 M)
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2 PROCEDURE Preparation of the apparatus. The instrument should be ready to use. If not, click on Exp1 icon on the desktop. The instrument is used in monitor mode only so you won’t need to access the mouse or keyboard at all. Verify that the Pressure sensor is connected to Channel 1 and the Temperature probe to Channel 2 . If not, ask your TA to check your setup. Clearly label three 125 mL erlenmeyer flasks (#1, #2, #3). Running the experiment with standard CaCO 3 . Place flask #1 on the analytical balance and press Re-zero. If your flask is wet, rinse it with a small amount of ethanol. The erlenmeyer flask must be clean and dry from the inside while the vial from the outside. If it is wet, the water will react with the antacid and release carbon dioxide before you are ready to collect it. Use a DRY spatula to transfer about 0.4 g of standard CaCO 3 into the flask. Record the precise weight in Table 1. Tap the flask gently to move the sample to the side of the flask. If you use more than 0.5 g of CaCO 3 , too much CO 2 will be produced, the pressure will exceed the capacity of the setup and that run will be unusable. If this happens during any of your runs, be sure to use a smaller sample in all further trials. However, using too small of a sample is also bad, as it will result in a small pressure change, which will be less accurate than you want. Fill a clean vial 3/4 "full" (6 mL) with 4.5 M HCl from the common burettes at the end of your aisle. Wipe any spilled acid from the outside of the vial, otherwise CO
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This note was uploaded on 04/04/2011 for the course SCIENCE CHEM 120 taught by Professor Fenster during the Winter '11 term at McGill.

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Exp1 - CO2 from antacid - CARBON DIOXIDE FROM AN ANTACID...

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