Copper Cycle Lab Report - Payton Rodgers

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Texas A&M University *

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119

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Chemistry

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Feb 20, 2024

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Reduce, Reuse, Recycle… Copper! 11/10/2022 CHEM 119-604 1 Payton Rodgers*, Brett Johnson Reduce, Reuse, Recycle… Copper! Introduction: The copper cycle is a very well-known and well researched cycle of reactions, as copper recycling has been happening for thousands of years. Copper itself is an anthropogenically used material that is used by both environmental scientists and resource economists, and there are many copper-based materials that have been recycled for a wide variety of applications used in our everyday lives. 1 This experiment was performed to identify reaction types from physical observations, and to practice writing net ionic equations and calculating percent yields by replicating the copper cycle through a series of steps. Experimental Summary: For this experiment, a 10 mL graduated cylinder was acquired and filled with 0.5 M of CuCl 2 and was transferred into a 125 mL Erlenmeyer flask. The graduated cylinder was rinsed with distilled water twice, and the rinse was discarded in a 250 mL waste beaker that was used for waste throughout the entire experiment. The same graduated cylinder was filled with 0.5 M of Na 2 CO 3 and then transferred into the 125 mL Erlenmeyer flask containing the CuCl 2 and swirled for 30 seconds. The graduated cylinder was rinsed twice again, and the rinse was discarded into the waste beaker. Then, a second 125 mL Erlenmeyer flask, a plastic funnel, and filter paper was acquired to set a gravity filtration apparatus. The filter paper was folded into a cone and stuck to the sides of the plastic funnel with a small amount of distilled water so it would stay throughout the filtration. The precipitate was poured into the second 125 mL Erlenmeyer flask using the funnel to be filtered. After the filtration was completed, the retained solid was transferred into a clean 150 mL beaker by carefully using a laboratory spatula to get all *Primary author 1 CDA UK. Recycling of Copper , Copper Development Association Inc. , 2022, https://www.copper.org/environment/lifecycle/ukrecyc.html.

the precipitate even the parts that remained on the filter paper. The filtrate was discarded into the waste beaker. The contents of the waste beaker were discarded to the waste container in the fume hood. Observations for this first step of the experiment were recorded. Moving onto the next step of the experiment, the precipitate was rinsed off the inner walls of the beaker with a few drops of distilled water, so it moved to the bottom. The beaker was placed onto a hotplate, secured with an iron ring, and covered with a watch glass. The hotplate containing an analog dial was set to a setting of 5. The precipitate was heated on the hotplate and stirred occasionally with a stir rod until it completed changed color. All observations were recorded for this step of the experiment. After the precipitate changed color, the beaker was removed from hotplate using beaker tongs and sat on the laboratory bench. For the third step of the experiment, it was required to wait for about 5 minutes for the beaker containing the precipitate to cool down. Then, the precipitate was moved to a clean 125 mL Erlenmeyer flask. The remnants of the precipitate in the 150 mL beaker were rinsed with 5 mL of water, and then added to the 125 mL flask to ensure that all the precipitate was transferred to the new flask. A clean 10 mL graduated cylinder was acquired and filled with 1 M of HCl and added to the 125 mL Erlenmeyer flask that contained the precipitate and stirred continuously for 2 minutes with a stirring rod, until the precipitate completely dissolved in the HCl. It turned from a murky brown color to a clear aqua color, and all observations were recorded. A 50 mL beaker was obtained and weighed, and the weight of this empty beaker was recorded to be 27.5637 grams, from an analytical balance. Moving onto step four of the experiment, the mixture was transferred to the pre-weighted 50 mL beaker and sat onto a stir plate. A magnetic stir bar was placed in the beaker, and the stir plate was set to a medium speed. Then, 0.3480 grams of Zn powder was measured using a weighing boat and an analytical balance, and this weight was recorded. The Zn powder was slowly added to the 50 mL beaker with continuous stirring. An additional 10 mL of HCl was measured out and added slowly as well. Once the reaction subsided, the stirring was stopped and about 5 minutes passed to allow for the precipitate to settle in the bottom of the beaker. At this point, Zn metal was still visible, so 1 M of HCl was added and stirred for an additional 5 minutes. At this point, no Zn metal was present, and 10 mL of distilled water was added and the magnetic stir bar was extracted from the precipitate with the magnetic retriever. The supernatant was decanted into the 250 mL waste beaker while ensuring that the precipitate was not discarded. For the final step of the experiment, the purification of precipitated copper, an additional 10 mL of distilled water was added to the 50

mL beaker to rinse the recovered copper, and then decantated to ensure again that the precipitate was not discarded. Then, the 50 mL beaker was placed on the hotplate at a setting of 5 and heated until the precipitate was dry. Once the recovered copper was dry, the hotplate was turned off and the beaker was removed from the hotplate with beaker tongs and placed on the lab bench to cool down for 5 minutes. Once cold, the beaker was reweighed on an analytical balance to determine the mass of the recovered copper, which was 28.0188 grams. The empty beaker mass was subtracted from the final mass of the beaker to determine the mass of the copper, which was .4551 grams. The copper was placed into the copper waste beaker in the hood, and the waste beaker contents were discarded into the inorganic waste container. Results and Calculations: Table 1. Table of all masses recorded throughout the experiment. Object Mass (g) Empty beaker mass 27.5637 Zinc mass 0.3480 Beaker and copper mass 28.0188 Final copper mass .4551 Table 2. Table of observations recorded throughout the experiment. Balanced Equation for Reaction Observations of Reaction CuCl 2 (aq) + Na 2 CO 3 (aq) à CuCO 3 (s) + 2 NaCl (aq) When the Na 2 CO 3 was added to the CuCl 2 , the texture of the mixture changed and bubbles that were tiny were formed. The mixture was thick. After filtered, the precipitate was gooey and sold. It was light blue. This reaction is classified as a double displacement reaction. CuCO 3 (s) à CuO(s) + CO 2 (g) As the precipitate was being heated, it started to bubble and about 2 minutes later it changed from light blue to green and dark brown. It

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looked like wet soil. This reaction is classified as a decomposition reaction. CuO (s) + 2 HCl (aq) à CuCl 2 (aq) + H 2 O (l) When the HCl was added, the brown precipitate almost immediately turned to a clear, aqua color and was liquid again and not thick. This reaction is classified as a double displacement reaction. CuCl 2 (aq) + Zn (s) à Cu(s) + ZnCl 2 (aq) The zinc turned black and started to clump up and expanded in size. The clumps were very solid. Then the blue color in the water started to go away. The water continued to get cleared until the clumps were completely copper colored and separated. The water was then evaporated, and we were left with copper. This reaction is classified as a single displacement reaction. Calculation for actual yield of copper Formula: Final beaker mass – empty beaker mass = actual yield of copper (copper mass) Equation: 28.0188 – 27.5637 .4551 Calculation for the percent yield of copper Formula: !"#$%#&’()*+,)*-*)&#. ,)*(-*)&#. ∗ 100 = % ࠵?࠵?࠵?࠵?࠵? Equation: .0112 4 .52665 4 ∗ 100 143% yield Discussion and Analysis: The purpose of this experiment was to be able to identify reaction types from physical observations, writing net ionic equations, and calculating percent yields. For the first reaction, the CuCl 2 which was a blue liquid reacted with NaCO 3 , a clear liquid. This reaction was

classified as a double displacement reaction, because there were only two reactants. The elements and groups in this reaction recombined, and the precipitates CuO, a thick blue solid, and NaCl, a clear liquid that was filtered out, were formed. The second reaction was classified as a decomposition reaction, because the thick reactant, CuCO 3 , produced two products, CuO and CO 2 , which was a murky brown mixture. The third reaction, which is where the CuO and CO 2 turned into a transparent aqua liquid, was also a double displacement reaction, since there was a reaction that occurred in water, and the products were an acid and base. The fourth reaction was classified as a single displacement reaction because a metal, which was ZnCl 2 , replaced a metal cation (Zn) from its salt. In the end, the percent yield calculated for this experiment was 143%. The reasoning for such a high percent yield is likely due to an error within the experiment. For example, there might have been excess zinc powder that was still remaining at the end of the experiment, or the measurements for each chemical used throughout the experiment could have been off, causing the percent yield to be higher than 100. A way to improve the results of the experiment could have been having more time so the amount of chemicals used could be measured to the exact amounts required. Safety concerns to consider for this experiment are when dealing with chemicals and glassware. Gloves and goggles must be worn at all times, and care must be taken to not spill chemicals or expose them to bare skin. Conclusions: This experiment was conducted to carry out the copper cycle and create copper from in order to use the results when identifying reaction types, writing net ionic equations, and calculating percent yields. The experiment was somewhat successful because copper was indeed created, but there was a larger percent yield than intended in the end. The data collected throughout the experiment led to an understanding of how chemical reactions can be identified from physical observations. References: UK, CDA. Recycling of Copper , Copper Development Association Inc., 2022, https://www.copper.org/environment/lifecycle/ukrecyc.html. (Accessed November 13, 2022)