Chemistry of Copper
An in depth report on the chemical reactions involving copper by Luke Van Horn
October 17, 2018
Ruch AT Chemistry C Band
Performed on September 27th, October 1st, and October 2nd with Emma Dietrich and Joe Petrini
Objective: The objective of the experiment is to observe the changes copper goes through as it reacts with various chemicals and to eventually get copper back into its original form without losing any copper in the process.
Data Analysis:
Masses of Before and After Experiment and Masses of Vessels
Original mass of copper
0.470 g
Day Two: Mass of evaporating dish and copper
48.185 g
Day Three: Mass of evaporating dish and copper
48.232 g
Mass of evaporating dish
47.427 g
Final mass of copper on Day Two
0.758 g
Final mass of copper on Day Three
0.805 g
Calculations:
Day Two: Mass of evaporating dish and copper = 48.185 g → 48.185 g - 47.427 g = 0.758 g
Final Mass of Copper on Day Two = 0.758 g
Day Three: Mass of evaporating dish and copper = 48.232 g → 48.232 g - 47.427 g = 0.805 g
Final Mass of Copper on Day Three = 0.805 g
_
Original mass of copper = 0.470 g
Mass of copper on Day 2 = 0.758 g
Mass of copper on Day 3 = 0.805 g
|V1 - V2| / ((V1 + V2)/2) = * 100%
Day Two: | 0.758 g - 0.470 g| / ((0.758 g + 0.470 g)/2) = 0.288 g/ 0.614 g = 0.469 → 46.9%
Percent difference between the original mass of the wire and the final mass of the
copper collected on Day Two = 46.9%
Day Three: |0.805 g - 0.470 g| / ((0.805 g + 0.470 g)/2) = 0.335 g/ 0.638 g = 0.525 g → 52.5%
Percent difference between the original mass of the wire and the final mass of the
copper collected on Day Three = 52.5%
Pre-Lab Questions:
I predict the final mass of the “recovered” copper will be lower than the original mass. I predict this because there is no copper being added into the system and thus the only way the “recovered” copper could have a higher mass is if there was something else mixed in with the copper when its mass was measured due to some error along the way. This would mean the copper’s mass would not have increased but that the sample being measured was not entirely copper. The added substance could be left over zinc or either of the two metals oxidizing. What I believe is more likely, is that through the chemical reactions and changes that the copper undergoes, some of it will be left behind thus having a lower mass when measured at the end. The copper seems to me to be especially at risk of being lost during the phase where the copper is a part of CuO. Some copper could get lost in the gravity filter as it’s unlikely that the students will get all of the copper off of the filters. It’s also likely that there will be some copper lost throughout the process because there are many containers used that the copper may stick to in trace amounts during transfers of solutions into other containers without the students noticing.
It is used in bleaching flour, in rocket fuel, and in the creation of some plastics (Encyclopedia, Nitrogen Dioxide). It is toxic and when inhaled, it can cause a number of respiratory problems such as coughing, wheezing, and trouble breathing. It also may increase the likelihood of the development of asthma and respiratory infections when exposed for long periods of time (EPA, Basic Information about Nitrogen Dioxide).
Only to the extent that you add enough nitric acid so that all of the copper can react with it without putting too much in so that the beaker would not be able to safely hold all of it and the solutions you plan to add in the future steps. The limiting reactant is the copper so as long as you add enough nitric acid that the copper can fully react with, the amount of excess nitric acid becomes irrelevant to the following reactions. You should be careful about recording the amount you put in because if something goes wrong during the experiment, you can see if it was the nitric acid that caused any problems.
Again, only to the extent that you add enough for the Cu(NO3)2 to react with without putting too much in that the beaker is unable to safely hold its contents. The Cu(NO3)2 is the limiting reactant so add enough for all the Cu(NO3)2 to be able to react. Also you need to add enough NaOH to react with all HNO3 because if there is HNO3 leftover than there is probably Cu(NO3)2 left over. There has to be enough NaOH that it reacts with all the Cu(NO3) and not just the HNO3. There should be an excess of NaOH so we know everything else has reacted.
Post-Lab Questions
1. Steps 2, 3, 4, 6, 7, and 8 involved chemical reactions; indeed, step 3 involved two separate but
related reactions. For each step, indicate the relevant balanced chemical reaction(s) integral to
the procedure at that point. Use state symbols, and please make sure to use proper typography.
Step 2. Cu(s) + 4HNO3 (aq) → Cu(NO3)2(aq) + 2NO2(g) + 2H2O(l)
Step 3. 2NaOH(aq) + Cu(NO3)2(aq) → 2NaNO3(aq) + Cu(OH)2(ppt)
Step 3. (cont’d) NaOH(aq) + HNO3(aq) → NaNO3(aq) + H2O(l)
Step 4. Cu(OH)2(s) + Heat → CuO(s) + H2O(l)
Step 6. H2SO4(aq) + CuO(s) → CuSO4(aq) + H2O(l)
Step 7. CuSO4(aq) + Zn(s) → Cu(ppt) + ZnSO4(aq)
Step 8. H2O(l) + 2HCl(aq) + Zn(s) → ZnCl2(aq) + H2(g) + H2O(l)
2. In a written paragraph, track the voyage of the copper through its many compounds and back
to metallic form. Although you do not need to recapitulate experimental procedure, describe all
relevant transformations. Indicate when copper is oxidized, and when it is reduced. Identify one
single-replacement reaction, one double-replacement reaction, one acid-base neutralization, and
one decomposition reaction.
The copper was first reacted with the HNO3 where the copper was oxidized to become Cu(NO3)2. The copper, now in the compound Cu(NO3)2, is reacted with NaOH and the copper is transformed into Cu(OH)2 from Cu(NO3)2. The excess HNO3 is also reacted with the NaOH in a acid-base neutralization reaction. Next, the Cu(OH)2 is heated until it breaks in CuO and water in a decomposition reaction. Then the CuO is reacted with H2SO4 in a double-replacement reaction to form CuSO4 and water. Zinc is added to the CuSO4 where the zinc replaces the copper to form ZnSO4 and copper in a single-replacement reaction. The copper is reduced and the zinc is oxidized. Finally, the copper is removed from the solution through decanting and drying where it is back in its original elemental form except that it is no longer a wire.
3. Why is it important to make sure your final system tested basic in Step 3? Think in terms of
the copper; not in terms of simply neutralizing the excess acid.
It is important for the final system to test basic in Step 3 because that means all of the Cu(NO3)2 has reacted with the NaOH. If the system is not basic, it means there is an excess of HNO3 and possibly Cu(NO3), but if the system is basic it means the NaOH has reacted with all the HNO3 and Cu(NO3) and there is now an excess of NaOH.
Conclusions:
The objective of the experiment was achieved to a certain extent. We were able to carry through the entire experiment and observe all the reactions and we lost minimal copper through the process. However, we had more copper at the end, 0.805 g, than in the beginning, 0.470 g, even though we never added more copper. We originally believed this was because not all the water and other liquids had evaporated from the copper when we weighed it, as it was 0.758 g, but this was not the case as the next day there appeared to be even more copper at 0.805 g. This could be due to trace amounts of zinc left over in the copper if we did not add enough HCl to react with it. We also may have not waited long enough for the HCl to completely react with the zinc. A set amount of time that one is required to wait after adding the HCl may be a helpful improvement in the future. The zinc or copper could have oxidized resulting in the increase in mass from Day Two to Day Three. However, there is inherent error in the nature of this procedure such as leaving the “recovered” copper out overnight where we don’t know what happens to it.
Percent Error: |V - E|/E *100%
Day Two: |0.758 g - 0.470 g| / 0.470 g = 0.693 * 100% = 69.3%
Day Three: |0.805 g - 0.470 g| / 0.470 g = 0.713 * 100% = 71.3%
A source of error from this experiment could have been the tendency of the copper to stick to the rubber policeman, beaker, and stirring rod throughout the experiment. However, this would have decreased the amount of copper recovered at the end, which was not the case. It did not have a significant impact on the massed “recovered” copper as the mass of the “recovered” copper was higher than that of the original copper. Another source of error could have been in Step 8. It does not specify how long one should wait for the zinc and HCl to react or what to look for to know all the zinc has reacted. If we did not wait long enough for the zinc and HCl to react, it would have increased the amount of recovered copper as there could be pieces of zinc left over in the recovered copper. This is probably the most significant source of error as it would have increased the measured mass, which is the result we observed. A different source of error could have been the oxidation of either the copper or the zinc or both. As the “recovered” copper, and whatever was included with it, was left out in the air, not in a solution, it gained mass. It went from 0.758 g to 0.805 g in a day showing an increase of 0.047 g. The copper and leftover zinc could oxidize in air overnight and gain oxygen ions, thus increasing its mass. This is likely what happened as well because this source of error would increase the measured mass on Day Three from Day Two, which is the result we observed. It is also worth mentioning that in our experiment, all of our CuO may not have reacted with all of of the H2SO4 because of our own human error and complications with decanting. This may have been a significant source of error although it would have reduced the amount of measured copper at the end not increased it, so it may have just decreased the amount of pure, not zinc, “recovered” copper despite the apparent “recovered” copper increasing in mass.
As discussed before, if Step 8 had given a set time or quality in the reaction to confirm all of the zinc had reacted, we may not have left zinc in our sample of copper and it would not have supposedly affected our data. Also controlling the environment of the lab could have been improved, such as keeping the “recovered” copper in a oxygen devoid environment, which would have limited the oxidation of the copper and zinc.
Works Cited
“Basic Information about NO2.” EPA, Environmental Protection Agency, 8 Sept. 2016, www.epa.gov/no2-pollution/basic-information-about-no2.
Encyclopedia.com. “Nitrogen Dioxide.” Chemical Compounds, Thomas Gale, 2006, www.encyclopedia.com/science/academic-and-educational-journals/nitrogen-dioxide.
An in depth report on the chemical reactions involving copper by Luke Van Horn
October 17, 2018
Ruch AT Chemistry C Band
Performed on September 27th, October 1st, and October 2nd with Emma Dietrich and Joe Petrini
Objective: The objective of the experiment is to observe the changes copper goes through as it reacts with various chemicals and to eventually get copper back into its original form without losing any copper in the process.
Data Analysis:
Masses of Before and After Experiment and Masses of Vessels
Original mass of copper
0.470 g
Day Two: Mass of evaporating dish and copper
48.185 g
Day Three: Mass of evaporating dish and copper
48.232 g
Mass of evaporating dish
47.427 g
Final mass of copper on Day Two
0.758 g
Final mass of copper on Day Three
0.805 g
Calculations:
Day Two: Mass of evaporating dish and copper = 48.185 g → 48.185 g - 47.427 g = 0.758 g
Final Mass of Copper on Day Two = 0.758 g
Day Three: Mass of evaporating dish and copper = 48.232 g → 48.232 g - 47.427 g = 0.805 g
Final Mass of Copper on Day Three = 0.805 g
_
Original mass of copper = 0.470 g
Mass of copper on Day 2 = 0.758 g
Mass of copper on Day 3 = 0.805 g
|V1 - V2| / ((V1 + V2)/2) = * 100%
Day Two: | 0.758 g - 0.470 g| / ((0.758 g + 0.470 g)/2) = 0.288 g/ 0.614 g = 0.469 → 46.9%
Percent difference between the original mass of the wire and the final mass of the
copper collected on Day Two = 46.9%
Day Three: |0.805 g - 0.470 g| / ((0.805 g + 0.470 g)/2) = 0.335 g/ 0.638 g = 0.525 g → 52.5%
Percent difference between the original mass of the wire and the final mass of the
copper collected on Day Three = 52.5%
Pre-Lab Questions:
- Predict whether the final mass of “recovered” copper will be lower or higher than your original mass. Explain why you made this prediction.
I predict the final mass of the “recovered” copper will be lower than the original mass. I predict this because there is no copper being added into the system and thus the only way the “recovered” copper could have a higher mass is if there was something else mixed in with the copper when its mass was measured due to some error along the way. This would mean the copper’s mass would not have increased but that the sample being measured was not entirely copper. The added substance could be left over zinc or either of the two metals oxidizing. What I believe is more likely, is that through the chemical reactions and changes that the copper undergoes, some of it will be left behind thus having a lower mass when measured at the end. The copper seems to me to be especially at risk of being lost during the phase where the copper is a part of CuO. Some copper could get lost in the gravity filter as it’s unlikely that the students will get all of the copper off of the filters. It’s also likely that there will be some copper lost throughout the process because there are many containers used that the copper may stick to in trace amounts during transfers of solutions into other containers without the students noticing.
- In Step 2, you produce nitrogen dioxide. Research NO2 on the Internet or in chemistry textbooks. When and where is it commonly produced outside the chemistry labs? What are the risks associated with it?
It is used in bleaching flour, in rocket fuel, and in the creation of some plastics (Encyclopedia, Nitrogen Dioxide). It is toxic and when inhaled, it can cause a number of respiratory problems such as coughing, wheezing, and trouble breathing. It also may increase the likelihood of the development of asthma and respiratory infections when exposed for long periods of time (EPA, Basic Information about Nitrogen Dioxide).
- Do you need to carefully measure and record the amount of nitric acid in Step 2? Explain your answer.
Only to the extent that you add enough nitric acid so that all of the copper can react with it without putting too much in so that the beaker would not be able to safely hold all of it and the solutions you plan to add in the future steps. The limiting reactant is the copper so as long as you add enough nitric acid that the copper can fully react with, the amount of excess nitric acid becomes irrelevant to the following reactions. You should be careful about recording the amount you put in because if something goes wrong during the experiment, you can see if it was the nitric acid that caused any problems.
- Do you need to carefully measure and record the amount of sodium hydroxide in Step 3? Explain your answer.
Again, only to the extent that you add enough for the Cu(NO3)2 to react with without putting too much in that the beaker is unable to safely hold its contents. The Cu(NO3)2 is the limiting reactant so add enough for all the Cu(NO3)2 to be able to react. Also you need to add enough NaOH to react with all HNO3 because if there is HNO3 leftover than there is probably Cu(NO3)2 left over. There has to be enough NaOH that it reacts with all the Cu(NO3) and not just the HNO3. There should be an excess of NaOH so we know everything else has reacted.
Post-Lab Questions
1. Steps 2, 3, 4, 6, 7, and 8 involved chemical reactions; indeed, step 3 involved two separate but
related reactions. For each step, indicate the relevant balanced chemical reaction(s) integral to
the procedure at that point. Use state symbols, and please make sure to use proper typography.
Step 2. Cu(s) + 4HNO3 (aq) → Cu(NO3)2(aq) + 2NO2(g) + 2H2O(l)
Step 3. 2NaOH(aq) + Cu(NO3)2(aq) → 2NaNO3(aq) + Cu(OH)2(ppt)
Step 3. (cont’d) NaOH(aq) + HNO3(aq) → NaNO3(aq) + H2O(l)
Step 4. Cu(OH)2(s) + Heat → CuO(s) + H2O(l)
Step 6. H2SO4(aq) + CuO(s) → CuSO4(aq) + H2O(l)
Step 7. CuSO4(aq) + Zn(s) → Cu(ppt) + ZnSO4(aq)
Step 8. H2O(l) + 2HCl(aq) + Zn(s) → ZnCl2(aq) + H2(g) + H2O(l)
2. In a written paragraph, track the voyage of the copper through its many compounds and back
to metallic form. Although you do not need to recapitulate experimental procedure, describe all
relevant transformations. Indicate when copper is oxidized, and when it is reduced. Identify one
single-replacement reaction, one double-replacement reaction, one acid-base neutralization, and
one decomposition reaction.
The copper was first reacted with the HNO3 where the copper was oxidized to become Cu(NO3)2. The copper, now in the compound Cu(NO3)2, is reacted with NaOH and the copper is transformed into Cu(OH)2 from Cu(NO3)2. The excess HNO3 is also reacted with the NaOH in a acid-base neutralization reaction. Next, the Cu(OH)2 is heated until it breaks in CuO and water in a decomposition reaction. Then the CuO is reacted with H2SO4 in a double-replacement reaction to form CuSO4 and water. Zinc is added to the CuSO4 where the zinc replaces the copper to form ZnSO4 and copper in a single-replacement reaction. The copper is reduced and the zinc is oxidized. Finally, the copper is removed from the solution through decanting and drying where it is back in its original elemental form except that it is no longer a wire.
3. Why is it important to make sure your final system tested basic in Step 3? Think in terms of
the copper; not in terms of simply neutralizing the excess acid.
It is important for the final system to test basic in Step 3 because that means all of the Cu(NO3)2 has reacted with the NaOH. If the system is not basic, it means there is an excess of HNO3 and possibly Cu(NO3), but if the system is basic it means the NaOH has reacted with all the HNO3 and Cu(NO3) and there is now an excess of NaOH.
Conclusions:
The objective of the experiment was achieved to a certain extent. We were able to carry through the entire experiment and observe all the reactions and we lost minimal copper through the process. However, we had more copper at the end, 0.805 g, than in the beginning, 0.470 g, even though we never added more copper. We originally believed this was because not all the water and other liquids had evaporated from the copper when we weighed it, as it was 0.758 g, but this was not the case as the next day there appeared to be even more copper at 0.805 g. This could be due to trace amounts of zinc left over in the copper if we did not add enough HCl to react with it. We also may have not waited long enough for the HCl to completely react with the zinc. A set amount of time that one is required to wait after adding the HCl may be a helpful improvement in the future. The zinc or copper could have oxidized resulting in the increase in mass from Day Two to Day Three. However, there is inherent error in the nature of this procedure such as leaving the “recovered” copper out overnight where we don’t know what happens to it.
Percent Error: |V - E|/E *100%
Day Two: |0.758 g - 0.470 g| / 0.470 g = 0.693 * 100% = 69.3%
Day Three: |0.805 g - 0.470 g| / 0.470 g = 0.713 * 100% = 71.3%
A source of error from this experiment could have been the tendency of the copper to stick to the rubber policeman, beaker, and stirring rod throughout the experiment. However, this would have decreased the amount of copper recovered at the end, which was not the case. It did not have a significant impact on the massed “recovered” copper as the mass of the “recovered” copper was higher than that of the original copper. Another source of error could have been in Step 8. It does not specify how long one should wait for the zinc and HCl to react or what to look for to know all the zinc has reacted. If we did not wait long enough for the zinc and HCl to react, it would have increased the amount of recovered copper as there could be pieces of zinc left over in the recovered copper. This is probably the most significant source of error as it would have increased the measured mass, which is the result we observed. A different source of error could have been the oxidation of either the copper or the zinc or both. As the “recovered” copper, and whatever was included with it, was left out in the air, not in a solution, it gained mass. It went from 0.758 g to 0.805 g in a day showing an increase of 0.047 g. The copper and leftover zinc could oxidize in air overnight and gain oxygen ions, thus increasing its mass. This is likely what happened as well because this source of error would increase the measured mass on Day Three from Day Two, which is the result we observed. It is also worth mentioning that in our experiment, all of our CuO may not have reacted with all of of the H2SO4 because of our own human error and complications with decanting. This may have been a significant source of error although it would have reduced the amount of measured copper at the end not increased it, so it may have just decreased the amount of pure, not zinc, “recovered” copper despite the apparent “recovered” copper increasing in mass.
As discussed before, if Step 8 had given a set time or quality in the reaction to confirm all of the zinc had reacted, we may not have left zinc in our sample of copper and it would not have supposedly affected our data. Also controlling the environment of the lab could have been improved, such as keeping the “recovered” copper in a oxygen devoid environment, which would have limited the oxidation of the copper and zinc.
Works Cited
“Basic Information about NO2.” EPA, Environmental Protection Agency, 8 Sept. 2016, www.epa.gov/no2-pollution/basic-information-about-no2.
Encyclopedia.com. “Nitrogen Dioxide.” Chemical Compounds, Thomas Gale, 2006, www.encyclopedia.com/science/academic-and-educational-journals/nitrogen-dioxide.