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Audrey Keith CHE 111-030 Gayan Kayunasingle Delaney Darland 1 Oct 2019 Determining the Calcium Makeup of Limestone through Gravimetric Analysis Introduction Limestone is made up of organic material that has gone through the process of lithification to for a solid rock. A major component of limestone is calcium carbonate, which is used in various products from chalk to cement (French, et al 76-77). To be able to use this compound in products and return a profit, it is necessary to isolate calcium carbonate from pieces of limestone with high percentages of calcium carbonate. There are two methods to determine the mass percent of calcium carbonate in a sample of limestone. One is creating carbon dioxide by adding an acid to the limestone piece, measuring the carbon dioxide that was created, and using stoichiometry to calculate the mass percent with the chemical equation: CaCO3 (s)+ HCl (aq )→CaC l2 (aq )+C O 2(g)+ H 2 O (l) The second method uses gravimetric analysis which compares the masses of two compounds composed of the same compound or element. This is possible because the mass of an ion in a pure compound always has a fixed ratio which can be used to find the mass percent of that same ion in an impure compound if the mass is known (Yonder). By precipitating and finding the mass of calcium in the sample, the mass of calcium carbonate in the original sample can be found through stoichiometry and the chemical equations: CaCO3 (s)+ HCl (aq )→CaC l2 (aq )+C O2(g)+H 2 O (l)

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N H 4 ¿2 S O4 (aq )→ CaS O4 (s)+2 N H 4 Cl (aq ) CaC l2 (aq)+¿ Using both methods and comparing the results will give insight into lab technique and how well the procedure was followed (French, et al 77). Methods The procedure can be found in the lab manual on pages 80-82. The only change is in step 19: do not scrape the sample off of the filter paper on the watch glass, keep the two together in the oven and while massing in step 20.

Works Cited French, April N., Allison Soult, Stephen Testa, Pauline Stratman, M. Meral Savas, François Botha, Carolyn Brock, Charles Griffith, Darla Hood, Robert Kiser, Penny

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O’Connor, William Plucknett, Donald Sands, Diane Vance, and William Wagner. “Experiment 4: Quantifying the Composition of Limestone.” General Chemistry Laboratory Manual. Plymouth: Macmillan Learning Curriculum Solutions, 2019. 75-82. Web. 1 October 2019.

Yonder, Claude. “Gravimetric Analysis.” Wired Chemist. Claude Yonder, 2019. Web. 1 October 2019....