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C103 Reactants and Products Lab

Indiana University
Uploaded: 5 years ago
Contributor: amairani2561
Category: Chemistry
Type: Report
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Filename:   Experiment 04.docx (57.57 kB)
Page Count: 4
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Transcript
Amairani Beltran, Lab Partner: Lindsey Meyers Chem C 103 1435 October 12, 2018 The Relationship between Reactants and Products Introduction In a chemical reaction, the amount of the starting reactants will always affect the amount of the final product produced. This is due to the limiting reagent, which is the first substance to be completely consumed. The goal of the experiment is to determine how varying amounts of reactants, in this case calcium chloride and sodium carbonate, affect the amount of product that is produced. After examining the relationship, we are then able to figure out the most efficient way to complete the chemical reaction and obtain the desired products. This is important because if the most efficient way to complete the reaction is not determined, then there is an unnecessary amount of waste that can be generated as a result. In order to complete this experiment, different amounts of calcium chloride were added to consistent amounts of sodium carbonate. Five different solutions were produced, each with a an increased amount of calcium chloride compared to the last. Once the solution was prepared, the precipitate was collected and analyzed. In order to determine the relationship between the reactants and product, the mass of the precipitate was calculated. After the limiting reagent has been completely consumed, the amount of product produced will plateau and eventually remain the same despite the increasing amount of calcium chloride added. Methods In order to complete the experiment, the following materials were obtained: Five 125 mL Erlenmeyer flasks Two graduated cylinders (10 mL and 25 mL) Glass stirring rod Buchner funnel Filter paper 500 mL suction flask with tubing Ring stand and clamp Distilled water Analytical balance 4 watch glasses 95% ethanol The experiment started off with the creation of a vacuum for the filtrate by assembling a suction flask with a Buchner funnel. The suction flask was connected to an aspirator at a fume hood sink with a rubber hose. This allowed for effective suction due to the sink’s high water pressure. A piece of filter paper was then placed in the Buchner funnel to collect the precipitate that was formed from the reaction. Next, the five Erlenmeyer flasks were cleaned using a small amount of 0.1 M HCL and distilled water. They were then labeled 1-5, each to be filled with varying amounts of CaCl2 and 25 mL of NaCO3. The following table indicates how much CaCl2 was added to each flask: Erlenmeyer Flask Number Amount of Cacl2 in mL 1 5 mL 2 15 mL 3 25 mL 4 35 mL 5 40 mL The mixtures were stirred thoroughly and the observations were recorded. Each solution was poured into the Buchner funnel and the precipitate was collected with the filter paper. During this time, 5 vials were labeled 1-5, each to be filled with the precipitate of the corresponding flask. Once the precipitate of each solution was dry, it was scraped off and placed in its assigned vial. The product was placed in a drying oven and a week later the mass of each was calculated and recorded. Results: Flask Number Mass of Vial 1 20.67 g 2 20.66 g 3 20.61 g 4 20.68 g 5 20.67 g Flask Number Mass of Vial + Precipitate 1 20.71 g 2 20.89 g 3 20.92 g 4 20.76 g 5 20.81 g Flask Number Mass of Precipitate 1 0.04 g 2 0.23 g 3 0.31 g 4 0.08 g 5 0.09 g In order to calculate the mass of the precipitate for flask 1, the mass of the vial (20.67 g) was subtracted from the mass of the vial with the precipitate (20.71 g). This process was repeated for each flask. Flask Number Mass of CaCl2 1 0.11 g 2 0.33 g 3 0.55 g 4 0.77 g 5 0.88 g In order to calculate the mass of CaCl2 in flask 1, the concentration (22 g/L) was multiplied by the amount of CaCl2 (5 mL) that was added to each flask and divided by 1,000 mL. This process was repeated for each flask. Balanced Equation: CaCl2 (aq) + Na2CO3 (aq) ? CaCO3 (s) + 2NaCl (aq) The graph for this experiment shows that the slope continuously raised with the first, second, and third flasks. This is because the sodium carbonate was introduced to the mixture. The slope then has a large, sudden decrease, indicating that the limiting reactant has been completely consumed. Afterwards, there is a relatively steady slope. Flask Number Moles of CaCl2 Moles of Na2CO3 1 0.00099 mol 4.9 x 10^-3 mol 2 0.0030 mol 4.9 x 10^-3 mol 3 0.0050 mol 4.9 x 10^-3 mol 4 0.0069 mol 4.9 x 10^-3 mol 5 0.0079 mol 4.9 x 10^-3 mol In order to calculate the moles of the CaCl2 in flask 1, the number of grams (0.11 g) was divided by the molar mass of CaCl2 (110.98 g/mol). To calculate the moles of Na2CO3, the 25 mL of the Na2CO3 was multiplied by 21 g/L. That calculation was then divided by the molar mass of Na2CO3 (105.9888 g/mol). Discussion: The objective of this experiment was to analyze the relationship between reactants and products and how the limiting reactant affects the final results. The process of investigation was conducted by creating a mixture of CaCl2 and Na2CO3. After the experiment was finalized, it was concluded that the limiting reactant at the beginning of the experiment was the CaCl2. The sodium carbonate then became the limiting reactant after the slope stopped increasing. This is because the precipitate that was produced remained the same. The graph created for this experiment demonstrates different results from the sample graph. This could be a result of multiple errors that may have been made during the experiment. The main error that could’ve led to this took place during the scraping of the precipitate from the filter paper. Often times when scraping the precipitate, the solid was not completely dry, meaning an excess amount of moisture was contained, thus affecting the mass of the products. In order to improve the results of the experiment, the precipitate should be fully dry and flaky before scraping takes place. The data was analyzed in such a way in order to evaluate how reactants yield products through double replacement. This reinforces the principle that the limiting reactants affect how much final product is produced. The balanced chemical equation allows for the demonstration of the mole ratio of reactants and products. The mole is useful in chemical equations because it serves as a unit of measurement and allows for conversion to take place. Reference: Dean, Norman. Robinson, Jill. “Chemistry 103 Laboratory Manual” Indiana University (2018). Indiana. Pg 4-1 to 4-10

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