Chemistry Lab 4 A Cycle of Chemical Reactions of Copper

Chemistry Lab 4 A - Walsh 1 Matthew Walsh Section 13 November 3 2009 A Cycle of Chemical Reactions of Copper Introduction Copper is a metallic

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Walsh, 1 Matthew Walsh Section 13 November 3, 2009 A Cycle of Chemical Reactions of Copper Introduction: Copper is a metallic element that can undergo an easily observable set of chemical reactions that pass copper from one chemical step to another in a cycle that both starts and ends as elemental copper. The process of these reactions is as follows: Cu(s) Cu(NO 3 ) 2 (aq) Cu(OH) 2 (aq) CuO(s) CuSO 4 (aq) Cu(s) A more detailed account of these reactions is given in the “Equations” section. Copper is easily dissolved in nitric acid and in concentrated sulfuric acid. This is important, because these two acids are used in the above-described cycle. It is equally important to note that there are many observable changes upon shifts between chemical steps in the cyclical reactions outlined above. This experiment highlights macroscopic changes in color, appearance, and bulk. As have been described, the lab’s purposes are: to understand classifications of reactions (as demonstrated in this experiment), to learn techniques for recording and interpreting macroscopic changes (such as those undergone by copper), and to practice quantitative laboratory techniques (for example, synthesis, separation, filtration, quantitative transfers) for minimalizing the loss of recovered copper. Experimental: The first deviation occurred when the copper had to be covered with 4.0 mL of nitric acid. Because the copper wire was not flattened to a full enough extent, much more than 4.0 mL was needed to submerge the copper wire. This led to using more sodium
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Walsh, 2 hydroxide than was called for in the lab manual (so that the sodium hydroxide could neutralize the nitric acid). So much sodium hydroxide was used that the solution needed to be transferred into a larger beaker, which was another deviation from standard procedure. The next deviation from the lab manual was that instead of using a Bunsen burner, wire gauze, et cetera to heat the solution of Cu(OH) 2 , a hot pad was used. Also, more Zn was added to the solution of CuSO 4 than the 2.0 g that was called for in the lab manual. On top of the 2.06 g, which was added in small increments, 0.28 g was added to fully react with the Cu 2+ . However, there was a period of time when another 10 mL of H 2 SO 4 was needed to dissolve the remaining Zn, so at some point there was unreacting solid Zn in solution with solid Cu due to a lack of acid. There were no further deviations from standard procedure. Data Analysis:
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This note was uploaded on 11/10/2009 for the course CHEM 11100 taught by Professor Mathews during the Spring '09 term at UChicago.

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Chemistry Lab 4 A - Walsh 1 Matthew Walsh Section 13 November 3 2009 A Cycle of Chemical Reactions of Copper Introduction Copper is a metallic

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