The aim of this experiment is to transform copper from one chemical state to another, ultimately converting it back to elemental copper. Throughout the process, we will make use of balanced chemical equations and employ quantitative laboratory techniques.
Procedure:
Obtain approximately 0.5 grams of copper wire. Rinse it with acetone to eliminate fingerprints, handle it with Kimwipes or tweezers, and weigh it. Place the wire in a 250 mL beaker in a fume hood. Add 7-8 mL of 16 M nitric acid, cover the beaker with a watchglass, and record observations.
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“ Laboratory Report: Conversion of Copper and Recovery to Elemental Form ”
Swirl the solution until copper completely dissolves. Add deionized water until the beaker is half full.
Gradually add 30 mL of 3.0 M sodium hydroxide. Test the solution's basicity with red litmus paper and record observations.
Heat the solution on a hot plate to near boiling while gently stirring to prevent bumping. Record observations. Continue heating for 5 minutes after the transformation, allowing the precipitate to coarsen. Remove from heat and warm 200 mL of deionized water for washing.
Let the precipitate settle to about ¼ of the liquid height. Decant the supernatant liquid into a clean beaker, avoiding loss of precipitate. Add the hot wash to the precipitate and decant again once settled.
Add approximately 4.5 g of zinc to the solution, covering the beaker with a watchglass. Stir vigorously and add more zinc if bubbling resumes until no bubbles form.
Remove unreacted zinc by decanting the liquid and adding 10 mL of 6 M hydrochloric acid. Heat the beaker until no gas evolves. Decant and wash the copper twice with 100 mL of deionized water.
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For the third wash, add 100 mL deionized water and boil gently for 5 minutes.
Weigh a clean, dry evaporating dish. Transfer the copper to the dish using a rubber policeman. Wash the copper once with 10-15 mL of methanol and twice with 10-15 mL of acetone. Decant the liquids.
Dry the copper over a steam bath, ensuring a slow heat to prevent explosive acetone evaporation. After the sample appears dry, wait a few minutes before drying the underside and weighing. Repeat this step once. Average the two weights if different and calculate the percent copper recovery.
This experiment illustrates the law of conservation of matter, emphasizing that matter cannot be created or destroyed. Thus, the final mass should match the initial mass. The underlying reactions involved include double replacement, single replacement, neutralization, and decomposition reactions, showcasing the diversity of chemical transformations.
Safety Precautions: When working in the laboratory, it is imperative to wear safety goggles. Additionally, given the use of nitric, sulfuric, and hydrochloric acid, extra precautions must be taken. Due to the potential for bumping during heating, regular stirring of the solution is essential.
Observations and Experimental Data:
Initial mass of copper wire: 0.688 g
Mass of evaporating dish plus dry copper: 42.752 g
Mass of empty evaporating dish: 42.156 g
Mass of recovered copper: 0.695 g
Percentage recovery: 101%
Cu + 4HNO3 → Cu(NO3)2 + 2H2O + 2NO2 Reaction type: Single replacement Observations: The wire dissolved, emitting a brown gas. The dissolved wire formed a green solution, which turned blue upon adding water. Solution composition after reaction completion: Copper and nitrate ions are dissolved in the aqueous solution.
Cu(NO3)2 + 2NaOH → Cu(OH)2 + 2NaNO3 Reaction type: Double replacement Observations: The solution initially turned green after adding sodium hydroxide, but stirring resulted in a darker blue shade and the formation of a thick precipitate.
HNO3 + NaOH → H2O + NaNO3 Reaction type: Neutralization Evidence of reaction occurrence: The solution emitted heat. Other components in the solution: Sodium and nitrate ions. Explanation for the bulkiness of the precipitate: The precipitate appears bulky due to its greater mass compared to the initial copper wire. Suspension in water also contributes to its perceived bulkiness.
Cu(OH)2 + heat → CuO + H2O Reaction type: Decomposition Observations: The solution turned black. Removed by washing/decantation in step 3: Sodium nitrate and excess sodium hydroxide.
CuO + H2SO4 → CuSO4 + H2O Reaction type: Neutralization Observations: The solution turned blue, and the precipitate dissolved. Components in the solution after step 4: Copper and sulfate ions.
Zn + CuSO4 → Cu + ZnSO4 Reaction type: Single replacement Observations: A reddish precipitate formed, and the solution became clear.
Zn + H2SO4 → H2 + ZnSO4 Reaction type: Single replacement Observations: The solution gained heat, and gas evolved. Evidence of reaction occurrence: Gas formation and increased temperature.
The objective of this experiment is to transform copper from one chemical state to another and eventually recover it in its elemental form. This process involves various chemical reactions, and our goal is to accurately classify and balance these reactions while documenting observations throughout the procedure. Additionally, we aim to practice quantitative lab techniques to determine the percentage recovery of copper.
Materials:
Copper wire (approximately 0.5 grams)
Safety goggles
Acetone
Kimwipes or tweezers
250 mL beaker
Fume hood
16 M nitric acid
Watchglass
Deionized water
3.0 M sodium hydroxide
Red litmus paper
Hot plate
6 M hydrochloric acid
Zinc (4.5 grams)
Evaporating dish
Rubber policeman
Methanol
Tables for weighing
Steam bath
Procedure:
Preparation of Copper Wire:
Obtain approximately 0.5 grams of copper wire.
Rinse the copper wire with acetone to remove fingerprints.
Handle the wire with Kimwipes or tweezers and weigh it.
Place the wire in a 250 mL beaker in the fume hood.
Add 7-8 mL of 16 M nitric acid, cover the beaker with a watchglass, and record observations.
Swirl the solution until copper has completely dissolved.
Add deionized water until the beaker is about half full.
Addition of Sodium Hydroxide:
Slowly add 30 mL of 3.0 M sodium hydroxide.
Test the basicity of the solution with red litmus paper and record observations.
Heating and Washing:
Heat the solution on a hot plate to near boiling while stirring gently.
Continue heating for 5 minutes after the transformation has taken place to coarsen the precipitate.
Remove the beaker from heat, let the precipitate settle, and decant the supernatant liquid.
Wash the precipitate twice with 100 mL of deionized water and once with 100 mL of boiling deionized water.
Zinc Reaction:
Add about 4.5 g of zinc to the solution.
Stir vigorously and add more zinc if bubbling recommences until no bubbles form.
Decant the liquid and add 10 mL of 6 M hydrochloric acid.
Heat the beaker until no gas evolves, decant, and wash the copper twice with 100 mL of deionized water.
For the third wash, add 100 mL deionized water and boil gently for 5 minutes.
Weighing and Transfer:
Weigh a clean, dry evaporating dish.
Transfer the copper to the dish using a rubber policeman.
Wash the copper once with 10-15 mL of methanol and twice with 10-15 mL of acetone.
Decant the liquids.
Drying Process:
Dry the copper over a steam bath, heating it slowly to prevent explosive acetone evaporation.
Wait a few minutes before drying the underside and weighing.
Repeat this step once, averaging the two weights if different.
Calculate the percentage copper recovery.
Calculations:
Percentage Recovery=(Mass of Recovered CopperInitial Mass of Copper Wire)×100%Percentage Recovery=(Initial Mass of Copper WireMass of Recovered Copper)×100%
Mass of evaporating dish plus dry copper: 42.752 g
Mass of empty evaporating dish: 42.156 g
Mass of recovered copper: 0.695 g
Percentage recovery: 101%
Chemical Reactions and Observations:
Cu + 4HNO3 → Cu(NO3)2 + 2H2O + 2NO2
Reaction type: Single replacement
Observations: The wire dissolved, emitting a brown gas. The solution turned green, then blue after adding water.
Solution composition after reaction: Copper and nitrate ions are dissolved in the aqueous solution.
Cu(NO3)2 + 2NaOH → Cu(OH)2 + 2NaNO3
Reaction type: Double replacement
Observations: The solution turned green initially, then a darker shade of blue with the formation of a thick precipitate.
HNO3 + NaOH → H2O + NaNO3
Reaction type: Neutralization
Evidence of reaction: The solution emitted heat.
Other components: Sodium and nitrate ions.
Cu(OH)2 + heat → CuO + H2O
Reaction type: Decomposition
Observations: The solution turned black.
Removed by washing/decantation: Sodium nitrate and excess sodium hydroxide.
CuO + H2SO4 → CuSO4 + H2O
Reaction type: Neutralization
Observations: The solution turned blue, and the precipitate dissolved.
Components in the solution after step 4: Copper and sulfate ions.
Zn + CuSO4 → Cu + ZnSO4
Reaction type: Single replacement
Observations: A reddish precipitate formed, and the solution became clear.
Zn + H2SO4 → H2 + ZnSO4
Reaction type: Single replacement
Observations: The solution gained heat, and gas evolved.
Evidence of reaction occurrence: Gas formation and increased temperature.
Zn + HCl → ZnCl2 + H2
Reaction type: Single replacement
Conclusion: The purpose of this experiment was successfully achieved by converting copper through a series of chemical reactions and recovering it in its elemental form. Throughout the procedure, each reaction was accurately classified, balanced, and observed. The reactions involved single replacement, double replacement, neutralization, and decomposition, showcasing the diversity of chemical transformations.
The law of conservation of mass was evident as the mass of the reaction was conserved, with any discrepancies likely attributed to experimental errors. The importance of patience and meticulous adherence to instructions was highlighted, contributing to minimal loss of copper.
Sources of Error:
The observed higher percentage recovery might result from adding excessive zinc, which could lead to unreacted zinc remaining in the final product.
Incomplete drying of copper before weighing could also contribute to a higher than expected percentage recovery.
Questions:
Low Percentage Recovery Possibilities:
Loss of copper during decantation.
Residual copper in the beaker after transfer to the evaporating dish.
Elevated temperature during weighing.
High Percentage Recovery Possibilities:
Incomplete removal of zinc.
Copper not completely dry during weighing.
See Attached for Calculations.
See Attached for Calculations.
A. Sodium Hydroxide Volume Calculation:
In Step 2, 30 mL of sodium hydroxide was added, but the calculated volume required for complete reaction was 23 mL. Excess sodium hydroxide was added to ensure all nitric acid and copper ions reacted.
Calculation: See attached.
B. Excess Sodium Hydroxide:
Excess sodium hydroxide was added in Step 2 to guarantee a basic solution and complete reaction of nitric acid and copper ions.
C. Consequences of Not Adding Enough Sodium Hydroxide:
Insufficient sodium hydroxide could lead to a low percentage recovery as some unreacted copper might be decanted.
This laboratory experiment not only provided valuable experience in classifying and balancing chemical equations but also offered a firsthand observation of elemental transformations. The meticulous nature of the instructions emphasized the need for patience, contributing to the successful execution of the experiment.
The sources of error highlighted potential areas for improvement, emphasizing the importance of precision in experimental procedures. Overall, the experiment served as an educational experience in practical chemistry applications, reinforcing fundamental concepts and skills.
Updated: Feb 29, 2024
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Laboratory Report: Conversion of Copper and Recovery to Elemental Form. (2024, Feb 29). Retrieved from https://studymoose.com/document/laboratory-report-conversion-of-copper-and-recovery-to-elemental-form
