Lab 6: The Chemistry of Copper Mike Fisher: Chem 111L-001
Data Table 1: Mass Measurement of Copper Sample
Initial Solid Copper Wire
Dry Büchner Top w/ #5 Whatman Filter
Final Sample Drying 1 in Büchner Top
Final Sample Drying 2 in Büchner Top
Final Sample Drying 3 in Büchner Top
Formulas and Equations:
Reaction 1: Cu(s) + 4 HNO3(aq) à Cu(NO3)2(aq) + 2 NO2(g) + 2 H2O(l)
Reaction 2: Cu(NO3)2(aq) + 2 NaOH(aq) à Cu(OH)2(s) + 2 NaNO3(aq)
Reaction 3: Cu(OH)2(s) + heat à CuO(s) + H2O(l)
Reaction 4: CuO(s) + H2SO4(aq) à CuSO4(aq) + H2O(l)
Reaction 5: CuSO4(aq) + Zn(s) à ZnSO4(aq) + Cu(s)
*No mathematical equations used
Mass copper final:
5.605 g – 5.217 g = 0.388 g Cu(s)
0.388 g/ 0.513 g *100% = 75.6 % recovery
Findings with Discussion:
75.6% of the copper sample was recovered. I am confident that the sample is dry because successive oven dryings and weighing yielded consistent mass. No zinc granules are visible in the final product, suggesting a pure copper sample. Some copper oxide was lost in the copper oxide filtration step. In addition, our dried sample ‘jumped’ due to some apparent static discharge causing some sample loss. Our percent recovery could be improved by washing the copper oxide step with the sulfuric acid and care to discharge static before handling the final dried sample.
Numbered Questions Within the Lab:*(not every lab includes such questions)
- The reaction between solid copper and nitric acid is exothermic. The resulting solution is warm to the touch.
- A blue/green color resulted from the nitric acid addition. Solid copper oxidized to Cu2+ in the copper (II) nitrate solution. All of the blue/green solutions must have this ion.
- The blue litmus paper turned red in the presence of a solution made acidic by the addition of nitric acid.
- A cloudy blue precipitate formed.
- The red litmus paper turned blue in the presence of basic sodium hydroxide.
- The blue litmus paper turned red in the presence of sulfuric acid.
- The solution is once again a blue to blue green color. The copper (II) ion must again be present to produce the color.
- 75.6% of the copper was recovered.
- Copper wire is cut into smaller pieces in order to increase surface area and speed up the oxidation reaction.
- Dissolving refers to ion solubility, or separation of ions with a polar solvent. It could also refer to non-polar solute and solvent interactions. In each case, solubility is a physical process. In our lab, Cu(s) oxidized to Cu2+ ion in the presence of HNO3. This represents a new species and a chemical change.
- NO3- and Na+ are the only ions present in the solution assuming that CuO(s) was filtered out and that the solution was neutralized prior to precipitation.
- b. Double Replacement
d. Double Replacement
e. Single Replacement
- Cu(s) is oxidized to Cu2+ ion in reaction one. In the same reaction nitrogen is reduced from a +5 oxidation state in HNO3(aq) to a +4 oxidation state in NO2(g).
- Rxn. 5: CuSO4(aq) + Zn(s) à ZnSO4(aq) + Cu(s)
In reaction five, solid zinc is oxidized from a neutral state to a +2 oxidation state in ZnSO4(aq). In the same reaction Cu2+ is reduced from a +2 oxidation state in CuSO4(aq) to a neutral oxidation state in solid copper.
- Our second filtration left a black copper oxide stain on the Whatman #5 filter. In addition, some of our dried final solid copper ‘jumped’ in contact with some static charge and was lost.
- Any water remaining in the sample after drying or zinc remaining after the hydrochloric acid addition would cause the final copper mass to measure high.
*Note: This example lab report conforms to the given lab. Please refer to How to Write an Informal Lab Report as well as your specific lab requirements.