The Copper Cycle
Wiley Turner
Liam Doyle, and Liam Springer
The Packer Collegiate Institute, 170 Joralemon Street, Brooklyn, New York, 11201
October 16th, 2017
Liam Doyle, and Liam Springer
The Packer Collegiate Institute, 170 Joralemon Street, Brooklyn, New York, 11201
October 16th, 2017
Objective:
The objective of this experiment was to put a certain amount of copper through a series of reactions and to, in the end, regain as much of that same copper as possible. Through this, we would be re-familiarizing ourselves with reaction types, experimental procedure, and experimental error.
The objective of this experiment was to put a certain amount of copper through a series of reactions and to, in the end, regain as much of that same copper as possible. Through this, we would be re-familiarizing ourselves with reaction types, experimental procedure, and experimental error.
Calculations:
15 Minutes after Reaction Calculations
Mass of Recovered Copper in Evaporating Disk: 52.084 grams
Mass of Empty Evaporating Disk with Label: 51.532 grams
52.084 grams - 51.532 grams = 0.552 grams
Recovered Mass of Copper: 0.552 grams
(0.552 grams - 0.530 grams)/(0.530 grams) x 100 = 4.15% difference between original mass of copper
and the recovered mass
Day after Reaction Calculations
Mass of Recovered Copper in Evaporating Disk: 52.064 grams
Mass of Empty Evaporating Disk with Label: 51.532 grams
52.064 grams - 51.532 grams = 0.532 grams
Recovered Mass of Copper: 0.532 grams
((0.532 grams - 0.530 grams)/(0.530 grams)) x 100 = 0.377% difference between original mass of copper
and the recovered mass
3 Days after Reaction Calculations
Mass of Recovered Copper in Evaporating Disk: 52.163 grams
Mass of Empty Evaporating Disk with Label: 51.532 grams
52.163 grams - 51.532 grams = 0.631 grams
Recovered Mass of Copper: 0.631 grams
((0.631 grams - 0.530 grams)/(0.530 grams)) x 100 = 19.1% difference between original mass of copper
and the recovered mass
Pre-Lab Questions
Post Lab Questions
Step 2: 4 HNO3 (l) + Cu (s) --> 2 NO2 (g) + 2 H2O (l) + Cu(NO3)2 (aq)
Step 3:
a) NaOH (aq) + HNO3 (aq) --> NaNO3 (aq) + H2O (l)
b) 2 NaOH (aq) + Cu(NO3)2 (aq) --> Cu(OH)2 (s) + 2 NaNO3 (aq)
Step 4: Cu(OH)2 (s) + heat --> CuO (s) + H2O (g)
Step 6: H2SO4 (aq) + CuO (aq) --> CuSO4 (aq) + H2O (l)
Step 7: CuSO4 (aq) + Zn (s) --> ZnSO4 (aq) + Cu (s)
Step 8: 2 HCl (aq) + Zn (s) --> H2 (g) + ZnCl2 (aq)
Conclusions:
Though our experiment was successful overall, there were some errors and unaccounted factors that may have altered our data and would explain the percent error of 4.15% between the original mass of copper and the ending mass of copper. One important source of error in our experiment that would account for a loss from the original amount to the final amount was the fact that the copper and the compounds containing copper were transferred through many different beakers and test tubes throughout the experience. This would account for a loss in copper in the end as every time the copper compound was transferred, there would always be some left over in the beaker even if it was a miniscule amount. Another source of error in our experiment was the fact that there may have been some left over zinc in our ending sample as the hydrochloric acid may have not reacted with all of it. This too would alter our ending mass as the copper would not be pure and would, in fact, contain zinc. Another aspect in our experiment that was puzzling was the fact that the copper actually gained mass by sitting out for days, drying. One explanation for this would be that, in sitting out, the copper oxidized with oxygen present in the air (2 Cu + O2 → Cu2O). Because an atom of oxygen is being added for every other copper atom during oxidization, this would explain the jump in mass of 0.099 grams from the final mass directly after the first drying and the final mass days after the drying.
In addition to fixing the errors, we could also improve the experiment in a couple ways. One idea would be to actually test the purity of the ending copper. This would make it so that we know how much copper we actually got out of the experiment. One idea to test this would be to recreate the copper (II) nitrate using pure copper along with our sample and using a spectrometer to shoot a wavelength and see how much light each one absorbs. This would have to be done by taking the same mass of copper sample and pure copper and reacting them both with a constant excess amount of nitric acid. If the nitric acid we use is in excess, the darker the copper (II) nitrate product is, the more pure the copper reactant would have been as copper (II) nitrate is blue in color. Because the darker solution would absorb more light, we would know that it has higher concentration of copper (II) nitrate and the starting copper would therefore be more pure. While this would be a valuable addition to the experiment, our lab was successful overall.
15 Minutes after Reaction Calculations
Mass of Recovered Copper in Evaporating Disk: 52.084 grams
Mass of Empty Evaporating Disk with Label: 51.532 grams
52.084 grams - 51.532 grams = 0.552 grams
Recovered Mass of Copper: 0.552 grams
(0.552 grams - 0.530 grams)/(0.530 grams) x 100 = 4.15% difference between original mass of copper
and the recovered mass
Day after Reaction Calculations
Mass of Recovered Copper in Evaporating Disk: 52.064 grams
Mass of Empty Evaporating Disk with Label: 51.532 grams
52.064 grams - 51.532 grams = 0.532 grams
Recovered Mass of Copper: 0.532 grams
((0.532 grams - 0.530 grams)/(0.530 grams)) x 100 = 0.377% difference between original mass of copper
and the recovered mass
3 Days after Reaction Calculations
Mass of Recovered Copper in Evaporating Disk: 52.163 grams
Mass of Empty Evaporating Disk with Label: 51.532 grams
52.163 grams - 51.532 grams = 0.631 grams
Recovered Mass of Copper: 0.631 grams
((0.631 grams - 0.530 grams)/(0.530 grams)) x 100 = 19.1% difference between original mass of copper
and the recovered mass
Pre-Lab Questions
- The mass of the recovered copper will be lower of that than the mass of the original copper due to experimental error. The original copper goes through so many reactions before returning to its original state, it is bound to lose some mass in the process, whether it is left in an unreacted reactant or a test tube. While this may be the situation in our experiment, it would not be the situation in an ideal world. In an ideal world, the same amount of copper that would go in would come out due to the law of conservation of mass. However, this is simply not possible in the real world as you will always lose some copper to error.
- Nitrogen dioxide is commonly produced by cars as they emit fumes from their engines. Cars originally emit nitrogen monoxide, this nitrogen monoxide bonds with atoms of oxygen from the air in order to create nitrogen dioxide. In addition, nitrogen dioxide is an intermediate in the industrial process of manufacturing nitric acid. This gas is very dangerous as it causes lots of damage to the environment including smog and acid rain which is extremely detrimental to the human population and the future of the planet. It can also cause respiratory problems and coming into contact with the gas can irritate skin and eyes.
- For this, you would not need precise measurements. This is because copper is the limiting reactant, so it is important that the nitric acid is in excess so that the entirety of the copper reacts with it. Because we know that it is a 4:1 ratio of nitric acid to copper in this reaction, and we know that there is 0.011 moles of copper present, there must be 0.044 moles of nitric acid present to fully react with the copper. However, there are 0.064 moles of nitric acid in the 4 mL of 16 M nitric acid solution that is suggested in the procedure, causing it to be in a large excess. Because of this, the measurements of nitric acid do not need to be precise as long as there are more than 0.044 moles of nitric acid present.
- A precise measurement is not needed for this reaction. The sodium hydroxide used in this step is for two reasons. To neutralize the remaining nitric acid from the previous step via an acid-base neutralization reaction and to react with the copper (II) nitrate via a double replacement reaction to create copper (II) hydroxide along with the byproduct of sodium nitrate. As long as there is enough sodium hydroxide to perform both of these reactions, the experiment will work. The excess sodium hydroxide also would not affect the experiment drastically, as it is dissolved in the water formed in step 3a and added in step 5. The water and sodium hydroxide solution would then be decanted and would no longer be present.
Post Lab Questions
Step 2: 4 HNO3 (l) + Cu (s) --> 2 NO2 (g) + 2 H2O (l) + Cu(NO3)2 (aq)
Step 3:
a) NaOH (aq) + HNO3 (aq) --> NaNO3 (aq) + H2O (l)
- Acid Base Neutralization
b) 2 NaOH (aq) + Cu(NO3)2 (aq) --> Cu(OH)2 (s) + 2 NaNO3 (aq)
- Double Replacement Reaction
Step 4: Cu(OH)2 (s) + heat --> CuO (s) + H2O (g)
- Decomposition Reaction
Step 6: H2SO4 (aq) + CuO (aq) --> CuSO4 (aq) + H2O (l)
- Double Replacement Reaction
Step 7: CuSO4 (aq) + Zn (s) --> ZnSO4 (aq) + Cu (s)
- Single Replacement Reaction
Step 8: 2 HCl (aq) + Zn (s) --> H2 (g) + ZnCl2 (aq)
- Single Replacement Reaction
- Throughout the experiment, the copper goes through many stages. In the first reaction, it bonds with the nitrate of the nitric acid to form an aqueous copper (II) nitrate along with byproducts of nitrogen dioxide and water. In this reaction, the copper is oxidized. From there, the copper (II) nitrate undergoes a double replacement reaction with aqueous sodium hydroxide to form aqueous sodium nitrate and solid copper (II) hydroxide. During the same step, the sodium hydroxide also reacts with the leftover nitric acid via an acid base neutralization to neutralize the solution. The copper (II) hydroxide is then heated and through a decomposition reaction it becomes water and solid copper (II) oxide. The copper (II) oxide is then heated and dissolved in sulfuric acid where it undergoes a double replacement reaction to form aqueous copper (II) sulfate and water. The copper (II) sulfate is then reacted with solid zinc and, through a single replacement reaction, reduces zinc to form aqueous zinc sulfate along with pure copper solid. Hydrochloric acid is added to the solution and reacts reaction with the remaining zinc to form hydrogen gas and aqueous zinc chloride in order to fully eliminate the zinc from the remaining solid copper.
- It is important that the solution tested basic in step three because it confirms that the copper (II) nitrate has been successfully reacted to form copper (II) hydroxide. Because copper (II) nitrate is not basic and the system tested as basic, we know that there has been copper (II) hydroxide formed. From this, we know that the copper (II) nitrate has truly gone through the double replacement reaction with sodium hydroxide to form the copper (II) hydroxide.
Conclusions:
Though our experiment was successful overall, there were some errors and unaccounted factors that may have altered our data and would explain the percent error of 4.15% between the original mass of copper and the ending mass of copper. One important source of error in our experiment that would account for a loss from the original amount to the final amount was the fact that the copper and the compounds containing copper were transferred through many different beakers and test tubes throughout the experience. This would account for a loss in copper in the end as every time the copper compound was transferred, there would always be some left over in the beaker even if it was a miniscule amount. Another source of error in our experiment was the fact that there may have been some left over zinc in our ending sample as the hydrochloric acid may have not reacted with all of it. This too would alter our ending mass as the copper would not be pure and would, in fact, contain zinc. Another aspect in our experiment that was puzzling was the fact that the copper actually gained mass by sitting out for days, drying. One explanation for this would be that, in sitting out, the copper oxidized with oxygen present in the air (2 Cu + O2 → Cu2O). Because an atom of oxygen is being added for every other copper atom during oxidization, this would explain the jump in mass of 0.099 grams from the final mass directly after the first drying and the final mass days after the drying.
In addition to fixing the errors, we could also improve the experiment in a couple ways. One idea would be to actually test the purity of the ending copper. This would make it so that we know how much copper we actually got out of the experiment. One idea to test this would be to recreate the copper (II) nitrate using pure copper along with our sample and using a spectrometer to shoot a wavelength and see how much light each one absorbs. This would have to be done by taking the same mass of copper sample and pure copper and reacting them both with a constant excess amount of nitric acid. If the nitric acid we use is in excess, the darker the copper (II) nitrate product is, the more pure the copper reactant would have been as copper (II) nitrate is blue in color. Because the darker solution would absorb more light, we would know that it has higher concentration of copper (II) nitrate and the starting copper would therefore be more pure. While this would be a valuable addition to the experiment, our lab was successful overall.
