Copper Cycle Lab Report PDF

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First Lab Report...

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Abstract: A series of experiments were done to observe copper being transformed into different forms as well as to observe the different types of reactions, and to determine the percentage recovered. The copper was exposed to other compounds in the solution and that exposure of copper brought abut the transformative reactions. Finally, the copper was returned back to its original state and the amount of the remaining material that was recovered was 77.7 %. Introduction: The reason for performing this series of experiments was to observe the five reactions involving copper. The three types of chemical reactions are the following: Precipitation reactions, acidbase reactions, and redox reactions. The precipitation reaction occurs when at least one soluble and one insoluble compound react in an aqueous solution which forms a solid known as a precipitate. An acidbase reaction, is when a hydrogen ion is transferred from one chemical substance to another chemical substance. The acid donates a hydrogen ion while the base receives a hydrogen ion. A redox reaction occurs when there is a transfer of electrons between two entities. The one gaining is considered to be reduced and the one losing is considered to be oxidized. There are five reactions to be observed which are shown as a balanced chemical equation. Reaction 1: Copper and aqueous nitric acid reacts with each other which leads to copper to transform from its original state to an ionic state through a redox reaction. 4 HNO3(aq) + Cu (s) →Cu(NO3)2(aq) + 2 H2O (l) + 2 NO2(g) Reaction 2: The copper transforms again, but this time from the Cu2+ into Cu(OH)2 through a precipitation reaction. Cu(NO3)2(aq) + 2 NaOH (aq) →Cu(OH)2(s) + 2 NaNO3(aq) Reaction 3: In this reaction, the Cu(OH)2 is heated and breaks down into copper oxide and water. Cu(OH)2(s) + heat →CuO(s) + H2O (l) Reaction 4: Solid copper reacts with sulfuric acid and then the copper returns to being Cu 2+ ion. The reaction is an acid base reaction. CuO(s) + H2SO4(aq) →CuSO4(aq) + H2O (l) Reaction 5: Copper and zinc exchange electrons and exchange physical states. The copper cycle is completed, because copper returns to its original form due to the redox reaction. CuSO4(aq) + Zn(s) →ZnSO4(aq) + Cu(s)

Data: Reaction 1: 4 HNO3(aq) + Cu (s) →Cu(NO3)2(aq) + 2 H2O (l) + 2 NO2(g) This reaction was the first of the series of reactions and at the beginning the copper was clearly a reddish brown color. The copper turned yellowish green when the nitric acid was introduced to the solution. Then the solution was bubbling and gas was released then it turned into a dark orange color. Then as more gas was released it become blue in color. Reaction 2: Cu(NO3)2(aq) + 2 NaOH (aq) →Cu(OH)2(s) + 2 NaNO3(aq) In this second reaction, when NaOH was added to the solution the blue became a darker blue and the solution thickened when the precipitation began. Reaction 3: Cu(OH)2(s) + heat →CuO(s) + H2O (l) In this third reaction, the solution darkened in color, due to the addition of heat and water. Then the solids appeared to separate apart from the liquid. All the liquid appeared to be towards the top of the beaker and the solids appeared to be closer to the bottom of the beaker. Reaction 4: CuO(s) + H2SO4(aq) →CuSO4(aq) + H2O (l) In this fourth reaction, the sulfuric acid was added. After the addition of the sulfuric acid, the solution turned light clear blue in color. The black solids were added into the solution. Reaction 5: CuSO4(aq) + Zn(s) →ZnSO4(aq) + Cu(s) This final reaction, when the zinc was added it caused the black solids to form. After a while the solids became more a reddish brown. After decanting the liquid was still light blue in color. After the addition of hydrochloric acid, the solution began to turn yellow. After the solution cleared, the remainder of the copper left over was rinsed with water and was clearly there as its original form.

Table 1. Initial and final masses of copper. Mass of Cu(g) Initial Mass Final Mass

0.497 g 0.386 g

Results: Table 2. The percentage of copper remaining after the reactions. Mass of Cu(g) Initial Mass Final Mass % Recover y

0.497 g 0.386 g

77.7%

Dividing the final mass of copper by the initial mass of copper and then multiplying it by two is how to figure out the percentage of recovery. % recovery = 0.386/0.497 * 100 % 77.7 % Discussion: The purpose of this was to observe the transformation of copper during each one of the five reactions. The first transformation of copper was achieved by the copper going through a redox reaction. The second transformation of copper was achieved by the copper going through a precipitation reaction. The third transformation of copper was achieved by decomposition. The fourth transformation of copper was achieved by copper going through an acid-base reaction. The final fifth transformation of copper, where copper eventually came back to its original form, was achieved by copper going through another redox reaction. Even though everything was measured out and all of the reactions that transformed copper were observed, not all the copper that was initially weighed was there at the end of the reactions. There are a few errors that could have caused this to happen. When the decanting was being done there was still some blue, which could point to a loss of some copper sulfate. Some of the solids might have been lost, which could have impacted the amount of copper, by in the end decreasing the amount....