Lab Report-Copper Cycle PDF

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A Cycle of Copper Reaction ABSTRACT The purpose of this experiment was to cycle copper through a series of different chemical forms by reacting the copper with different chemicals. The percent recovery came out to be 17%. INTRODUCTION The purpose of this experiment was to cycle copper through five different reactions. The different chemical reactions were precipitation reactions, acid-base reactions, and oxidation-reduction (or redox) reactions. Precipitation reactions occur when two solutions containing soluble salt form an insoluble salt when combined and can help determine the amount of ions in the solution. Acid-base reactions happen when there is an exchange of H+ ions with a solution that is neutral or electrically charged and can be used to determine pH. Oxidation-reduction (redox) reaction is when there is a transfer of electrons. The balanced equation of reaction 1 was 4HNO3(aq) + Cu (s) →Cu(NO3)2(aq) + 2 H2O (l) + 2 NO2(g) and was an oxidation-reduction reaction. The balanced equation of reaction 2 was Cu(NO3)2(aq)+2NaOH (aq) →Cu(OH)2(s) + 2 NaNO3(aq) and has a precipitation reaction. Reaction 3 was Cu(OH)2(s) + heat →CuO (s) + H2O (l) and was a bit different because Cu(OH)2(s) is known for being thermally unstable and in this specific reaction, heat was used instead of any other chemical to create a reaction. The balanced chemical formula of reaction 4 was CuO(s)+H2SO4(aq) →CuSO4(aq) + H2O (l) and was an acid-base reaction. The balanced formula for reaction 5 was CuSO4(aq) + Zn (s) →ZnSO4(aq) + Cu (s) and was an oxidation-reduction reaction. DATA Table 1: Initial and Final Copper Masses Mass of Copper (g)

0.479 g

Mass of Copper Retrieved (g)

0.082 g

Table 2: Balanced Equations and Observations Reaction 1: 4 HNO3(aq) + Cu (s) →Cu(NO3)2(aq) + 2 H2O (l) + 2 NO2(g)

Observations: Almost immediately after adding the nitric acid the copper began to dissolve and release nitrogen dioxide in the form of dark orange steam and turned the solution a teal/ blue color.

Reaction 2: Cu(NO3)2(aq)+2NaOH(aq)→Cu(OH)2(s)+2 NaNO3(aq)

Observations: The blue solution turned chunky as soon as the NaOH came in contact with the solution. It looked like a lava lamp. After letting the solution sit, the solution had a mucus-like concentration.

Reaction 3: Cu(OH)2(s)+heat→CuO(s)+H2O(l)

Observations: When we put the solution on the hot plate the solution turned black around 2 minutes of the heat. Water was added to the concentration and began forming a supernatant layer at the bottom of the beaker.

Reaction 4: CuO(s)+H2SO4(aq)→CuSO4(aq)+H2O(l)

Observations: When the solution came in contact with the sulfuric acid the solution turned back into the similar blue hue that was observed in reaction 1.

Reaction 5: CuSO4(aq)+Zn(s)→ZnSO4(aq)+Cu (s)

Observations: Zinc was added, turning the solution a grey color. After decanting, hydrochloric acid and water were added and made red petal-like shapes similar to reaction 2.

RESULTS Percent recovery = (mass of copper recovered/initial mass of copper) *100% = (0.082g/.479g)*100 = (0.171)*100 = 17% The calculated percent recovery of copper is 17% DISCUSSION In reaction 1 there is a redox reaction from Cu to Cu2, reaction 2 was a precipitation reaction that went from Cu2 to (Cu(OH)2, reaction 3 decompose the (Cu(OH)2 solution into CuO by using heat in the form of an iron plate, reaction 4 had acid-base reactions and made CuO into Cu2, finally reaction 5 had a redox reaction back into copper from Cu2. After  the final product is collected, the solution was decanted and put on a hot oven to evaporate the water that was

present so the copper would be the only thing left was the copper. Throughout the experiment there was some heat produced at the bottom of the beaker indicating a chemical reactions. This happens because chemical reactions involve the breaking and formation of chemical bonds, but to break a chemical bond it takes energy which is released through heat. Another indicator of a chemical reaction was the different physical properties they all portrayed when adding a different chemical. Some turned to ooze (reaction 2), and others changed the solution to a different color (reaction 1). When  finding out the mass of the retrieved copper there was an issue with the original mass of the beaker and the mass of the beaker with the copper. The original mass of the beaker was 84.6g, but when the beaker with the retrieved copper was weighed the mass of the beaker turned out to be 84.9g which should have instead been less than the original mass, so something was wrong. To fix this issue the copper was instead weighed using a weigh boat. The weigh boat was 0.562g and the mass of the copper that was left in the beaker was 0.644g. The amount of copper retrieved was 17% which isn’t exactly a lot of copper, but this can be explained because of the decanting process. Towards the end of reaction 5, the instructions stated to decant 3 times and in these sessions, there was a loss of copper....