Experiment 3: Separating and Determining the Mass of Calcium Ion in a Calcium-Enriched Tablet
In this lab, we dissolved a calcium-enriched tablet and participate the calcium ion as calcium carbonate. Our purpose is to determine the masses of calcium carbonate and calcium ion, to determine the mass percent of calcium ion in the tablet and to compare the masses and the percent with the listed tablet ingredients. This time we used a 150mL beaker, analytical balance, forceps, a 50mL graduated cylinder, a glass rod, beaker tongs, a hot plate, two 16 x 125-mm test tubes, centrifuge, a medicine dropper, a filter paper, a filter funnel, a 250-mL Erlenmeyer flask, a watch glass, a drying oven, a spatula and a red litmus paper. The chemicals we need were 20mL of 2.0M HCl, a calcium-enriched tablet and 25mL of 1.0M Na2CO3 solution. At the very beginning we weighed the calcium-enriched tablet and the weighing paper, after recording the masses, we added the hydrochloric solution to the beaker with the calcium tablet in it. The calcium dissolved really quickly and there were bubbles and foams formed. We then heated the beaker with a hot plate for 2 to 3 minutes, equally distributed the supernatant solution into two test tubes, but avoid pouring the solid. After centrifuging the samples, we added extra HCl solution into the test tubes, there wasn’t any bubbling occurs, so we could continue and put the mixtures into the centrifuge again. And then put the NaCO3 solution into the beaker and wait to allow the CaCO3 precipitate to form. We then tested whether the supernatant solution is still acidic with a piece of red litmus paper, filter the liquid and we had some CaCO3. Dried the filter paper and CaCO3 in the oven, then we broke the CaCO3 into small particles with a glass rod, and dried it one more time. Let it cool and repeat heating, cooling and weighing it until the masses differ between two results are less than 0.01g. The percent yield is 25%, which is really off....
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