Experiment #28

The Copper Cycle

Lara El SaidCHEM 112-500Experiment performed: March 29th 2015

Introduction

In this experiment a series of reactions involving copper were performed in order to yield the copper cycle. Copper was used at the beginning and then undergoes several reactions that recover the copper into solid copper [3]. Therefore the experiment is a copper cycle since the reaction starts with copper and ends up with also copper. The best yield is to have the same amount of copper that the experiment started with which not to have any copper lost or gained at the end of the experiment. By this, the experiment would show the law of conservation of mass. Therefore the percent yield, by using the mass of copper at the beginning and mass of the copper at the end is calculated, in order to know how much copper was lost. Tests were performed to test the reaction of copper with four different compounds as well as the solubility of copper compounds. The properties of coppers reaction was tested with four solutions which gave four different copper compounds that are in the copper cycle which are: copper (II) nitrate, copper (II) hydroxide, copper (II) oxide, and copper (II) sulfate based on the tests performed. Some of the main techniques applied in this experiment were weighing the masses of copper, heating the reactions, and filtering. Figure 1: Copper CycleHeatHSOZnHNO

NaOHCopper Cycle

Procedure

The procedure of the experiment can be split into two parts. The first part of the experiment was the preliminary tests part where Cu strips were placed into 4 different test tube. Each test tube was filled with different solutions. These solutions were 3 M HCl, 6 M NaOH, 6 M HNO3, and 2 M H2SO4. These solutions were added to the Cu strips and the observations were recorded. Four other test tubes were obtained but this time the tubes had the copper salts: CuSO4, Cu(NO3)2, CuO and Cu(OH)2. These salts were used to test the solubility of the compounds by dissolving these salts with about 10 mL of distilled water and again observations were recorded.The second part of the experiment was the copper cycle part. After calculations were done it was found that 0.2 grams of copper should be placed in a 250 mL beaker along with 2.1 mL of 6 M HNO3 should be poured into the beaker. After a reaction between copper and HNO3 occurred, about 1.1 mL of 6 M NaOH was added to the Cu(NO) solution. Then the solution was tested whether it is acidic or basic by using litmus paper. Now the Cu(OH)2 solution was heated by using the hot plate stirrer until it started to boil. Once it started to boil the reaction was put aside to cool down a bit. Then the solution was filtered in a beaker by using a vacuum filtration in order to separate the solid Cu(O) from the solution. When filtration was done, the solid Cu(O) that was on the filter paper was removed by pouring about 1.6 mL of H2SO4 onto the filter paper under a beaker in order to get the CuSO4 solution in the beaker. At the end 0.2 grams of metallic zinc powder was added to the solution. 3M of HCl was added to the solution to avoid any excess of zinc. After the solution was filtered, solid copper was extracted and weighed to compare it with the original amount of copper used. [1]

ResultsPreliminary Tests:Metallic Copper with:Reaction occurredObservations

HClNoNothing

HNOYesTurned warm, brown gas was formed, bubbles were released, solution turned into blue colour

NaOHNoNothing

HSONoNothing

When copper strips were placed with HCl, NaOH, HSO nothing was observed therefore it was concluded that a reaction didnt occur, as for HNO there were changes that occurred which shows that a reaction has occurred.

Solubility Tests:CuSOSoluble (turned into light blue color)

Cu(OH)Insoluble (Dark blue almost black color)

Cu(NO)Soluble (light blue in color)

Copper Cycle:Procedural SetupColor ObservedComments and Observations

Copper added to HNOFrom colorless into reddish brownNO gas as well as water vapor were released

NaOH addedSolution became dark blue-

Heating solutionColor turned to blackBubbles formed when the solution started to boil

After filtering and addition of HSOColor turned into light blue-

Zn was addedTurned greenBubbles were released

During the copper cycle many reactions occurred and each reaction had different colors observed at the end the collected mass of metallic copper was 0.135 grams which shows that copper was lost but the percent yield we had was 67.5%.

Discussion

All the results that were obtained in this experiment were predictable according to the tests that were performed at the beginning. For example when NaOH was added to copper it was predicted that the solution would be Cu(OH) since a blue color of the solution appeared and that is true since according to the preliminary tests the Cu(OH) solution turned into a dark blue which was almost a black color. As for the HSO when added to the filtered solution, Cu(SO) was obtained which also had a blue color but a light blue color. All four reactions that are in the copper cycle occurred. The copper cycle was proved according to the product that was produced which was metallic copper.For copper cycle to take place the reactant as well as the product of the reaction should be copper. But since the percent yield was 100% therefore the same amount of copper was not conserved instead there was a 67.5% yield [2]. Copper was lost, the reason might be because not all of the reactions went to completion which have caused the reactions not to obtain the theoretical amount of copper. If the reactions went to completion then the percent yield would have been 100%. Some other sources of error were that while filtration not all copper were filtered or weighing the copper or zinc accurately. But at the end of the experiment the copper cycle was proved since we started with copper and ended up with copper.When HNO, NaOH, Zn were added reaction occurred and changed the colors of the solution as stated in the results part as well as when filtration occurred and heating the reaction. All of these actions had to do with reacting with copper which was extracted at the end.

Conclusion

The objective of this experiment was fulfilled in this experiment since the copper cycle was proved, by starting with copper and finishing the experiment with the product copper. According to Figure2. It is shown that reactions occurred with the solutions Cu(NO), Cu(OH), and CuSO to end up with the metallic copper product. But the copper wasnt completely retrieved as mentioned before due to some error such as filtration or even the equilibrium error as mentioned before the reaction doesnt go to completion. Copper CycleFigure 2: Reactions involved in the copper cycle

Work Cited:

[1] The Copper Cycle Experiment - A Series of Reactions. Retrieved April 5, 2015, fromhttps://www.youtube.com/watch?v=tyrne4AFOvY

[2] Conservation of mass: A cycle of copper reactions. (n.d.). Retrieved April 5, 2015, from http://archives.evergreen.edu/webpages/curricular/2000-2001/genchem2001/copperlab.html

[3] Copper Cycle. Austin Peay State University Department of Chemistry. Retrieved April 5, 2015, fromhttps://www.apsu.edu/files/chemistry/COPPER_CYCLE_S10.pdf