Quantifying the Composition of Limestone PDF

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Sharlene Wang CHE 111-013 Xiaojing Wang Maggie Almsari 24 February 2020

Determining the Configuration of Limestone Introduction: The goal of this experiment is to see how much calcium carbonate is present in limestone samples. Limestone makes up for about “10% of all sedimentary rocks on earth’s surface” (French 72-82). But limestone is even more common in Kentucky which “makes up more than 50% of surface rocks in Kentucky” (French 72-82). For a surface rock to be considered limestone, it has to have at least 50% of dolomite and calcite present (French 75-82). Limestone bubbles when an acid is added to the solution which then releases carbon dioxide. This can be shown from the equations below: CaCO3(s) + 2HCl(aq) → CaCl2(aq) + H2CO3(aq) HCO3 (aq) → CO2(g) + H2O(l) By using stoichiometry, you can determine the total of calcium carbonate in the sample. The carbon dioxide produced in Step 2 which only came from the carbonic acid that was produced in Reaction 1. As a result, the amount of carbon dioxide produced back to the original calcium carbonate which was in Reaction 3.

We can also measure how much calcium carbonate by finding out how much calcium ion is in a limestone sample. To figure this out, we have to react the solution with ammonium sulfate to produce mineral gypsum in the following equation:

CaCl2(aq) + (NH4)2SO4(aq) → CaSO4(s) + 2NH4Cl(aq)

By using stoichiometry, you can determine how much calcium sulfate it produces through this reaction. Therefore, we can work our way back to how much calcium ion was in the original sample and thus the amount of calcium carbonate. The purpose of this experiment is to find out the percent composition of limestone, to find it, you have to use the equation below: mass % of A= mass of A/ total mass of substance *100 Another purpose is to have knowledge of Gravimetric Analysis which is how the element forms into a compound known as a precipitating agent. The solid is then isolated and weighed to see how much of the compound is in the sample. To execute Gravimetric Analysis, you need to know how to do filtration. Filtration is a process that separates soluble and insoluble compounds. Another role that this experiment is trying to teach is the pH indicators. pH indicators are “molecules that react to specific and small changes in pH by physically changing color with their protonation or deprotonation” (French 75-82).

Procedure: No changes were made. (French 75-82)

Works Cited French April N., Alison Soult, Stephan Testa, Pauline Stratman , M. Meral Savas, Francois Botha, Carolyn Brock, Charles Griffith, Darla Hood, Robert Kiser, Penny O’Connor, William Plucknett, Donald Sands, Diane Vance, William Wagner. “Experiment 4: Quantifying the Composition of Limestone.” General Chemistry Laboratory Manual Hayden-Mcneil Lab Solutions. 2019-2020. 75-82. Web. University of Kentucky. 23 February 2020....