Copper Cycle Lab Report

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Jun 13, 2024

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The Copper Cycle Samantha Delaunay Cory Silguero The University of Texas at Austin 1 P. Sotelo SP2024

Redox reactions stand as prominent methods for producing valuable compounds. In light of increasing awareness of green chemistry, there's been a search for sustainable routes to redox reactions. This has led to significant interest in photoredox catalysis, a burgeoning field where molecules undergo oxidation or reduction using visible light – a vast natural resource. This tutorial paper offers an introductory overview of photoredox catalysis, accompanied by select examples, with the aim of inspiring further exploration and advancement in this rapidly evolving research domain. In a comprehensive study, researchers investigated the oxygen redox reaction and structural reversibility of NCM or NCA, promising cathode materials for high-energy-density Li- ion batteries. Utilizing synchrotron X-ray absorption spectroscopy, scanning transmission electron microscopy, and density functional theory calculations, they uncovered that oxygen redox occurs due to cation mixing upon delithiation, despite the absence of Li-O-Li configurations in its pristine form. The formation of the I41 structure was linked to the migration of transition metals in deeply delithiated material, extending the phase transformation route from layered to rock-salt structure. These findings deepen the understanding of oxygen redox and its impact on structural transformations in Ni-rich layered oxides, offering insights for enhancing cathode material performance in next-generation Li-ion batteries. Antoine Lavoisier's dedication to precise measurement was evident in his meticulous experiments. In one experiment, burned phosphorus and observed the formation of a white flaky product. Although the phosphorus, the reactant in this case, was not soluble in water, the product was. Therefore, he collected the product, separating it from the unreacted phosphorus through thorough washing with water. After drying, he could measure the amount of phosphorus that had burned, the quantity of oxygen consumed, and the mass of the resulting product. Through his experiments, he consistently found that the mass of the product equaled the sum of the masses of the consumed reactants. This discovery laid the foundation for the law of conservation of mass. Examining the Hindenburg disaster of 1937 provides a chemical perspective on oxidation-reduction reactions. The dirigible, filled with hydrogen, utilized this gas to maintain buoyancy. Unfortunately, during its voyage from Germany to the United States, the airship met a tragic end due to the explosive reaction between hydrogen and oxygen. In this event, hydrogen lost electrons, undergoing oxidation, while oxygen gained electrons, experiencing reduction. Metallic copper will undergo a sequence of reactions with different reagents to generate four distinct copper compounds, followed by its restoration to its original metallic state. Each reaction's chemical and physical alterations will be observed and documented, with balanced chemical equations being formulated and categorized. The final step involves determining the percent recovery of the initial copper product. 2 P. Sotelo SP2024

Table 1. Initial and final masses of Cu (s). Description Mass (g) Cu (s) wire 0.361 Evaporating dish 25.906 Evap. dish + Cu (s) product 26.193 Cu (s) product 0.287 Table 2. Observations for Reactions 1-5. Reaction Product Observations 1 Cu(NO 3 ) 2 Emits brown gas, turns a blue color 2 Cu(OH) 2 Neon/bright blue, pH paper is blue on first test 3 CuO Bright blue to dark blue to black cloud 4 CuSO 4 Light blue, burnt Cheeto wire 5 Cu (s) Orange copper precipitate, stinky 3 P. Sotelo SP2024

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For the first step of the copper cycle, copper metal (Cu) reacts with nitric acid (HNO3) to form copper(II) nitrate (Cu(NO3)2). The initial reddish-brown metallic copper turns into a blue solution of copper(II) nitrate. Figure 1: End of Step 1 Copper Cycle Next, Copper(II) nitrate (Cu(NO3)2) reacts with sodium hydroxide (NaOH) to form copper(II) hydroxide (Cu(OH)2) A blue solution of copper(II) nitrate reacts with colorless sodium hydroxide to form a blue-green precipitate of copper(II) hydroxide. Figure 2: End of Step 2 Copper Cycle 4 P. Sotelo SP2024

Thirdly, Copper(II) hydroxide (Cu(OH)2) decomposes upon heating to form copper(II) oxide (CuO). The blue-green liquid of copper(II) hydroxide turns into a black solid of copper(II) oxide with a clear liquid. Figure 3: End of Step 3 Copper Cycle After this, Copper(II) oxide (CuO) reacts with sulfuric acid (H2SO4) to form copper(II) sulfate (CuSO4) and water (H2O). The black solid of copper(II) oxide dissolves in the sulfuric acid solution to form a blue solution of copper(II) sulfate. Figure 4: End of Step 4 Copper Cycle 5 P. Sotelo SP2024

Finally, Copper(II) sulfate (CuSO4) reacts with metallic aluminum (Al) to form metallic copper (Cu). The blue solution of copper(II) sulfate reacts with metallic aluminum to deposit metallic copper onto the aluminum surface and the liquid will become more clear as the copper forms. Figure 5: End of Step 5 Copper Cycle The formation of precipitates in some reactions is attributed to the low solubility of certain copper compounds. Insoluble or sparingly soluble compounds tend to precipitate out of solution, whereas soluble compounds remain dissolved. Step 1 is a redox reaction, step 2 is a precipitation reaction, step three is a decomposition reaction, step 4 is an acid-base reaction, and step 5 is also a redox reaction. Their according chemical equation requirements are described below. Step 2 Precipitation Reaction: Balanced Formula Unit: Cu(NO 3 ) 2 (aq) + 2 NaOH (aq) → Cu(OH) 2 (s) + 2 NaNO 3 (aq) Total Ionic: Cu +2 (aq) + 2 NO 3 - (aq) + 2 Na + (aq) + 2 OH - (aq) → Cu(OH) 2 (s) + 2 Na + (aq) + 2 NO 3 - (aq) Net Ionic: Cu 2+ (aq) + 2 OH - (aq) → Cu(OH) 2 (s) Step 4 Acid-Base Reaction: Balanced Formula Unit: CuO (s) + H 2 SO 4 (aq) → CuSO 4 (aq) + H 2 O (l) 6 P. Sotelo SP2024

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Total Ionic: CuO (s) + 2 H + (aq) + SO 2- 4 (aq) → Cu 2+ (aq) + SO 2- 4 (aq) + H 2 O (l) Net Ionic: CuO (s) + 2 H + (aq) → Cu 2+ (aq) + H 2 O (l) Step 3 Decomposition Reaction: Balanced Chemical Equation: Cu(OH) 2 (s) → CuO (s) + H 2 O (1) Step 1 Redox Reaction: Balanced Chemical Equation: Cu (s) + 4 HNO 3 (aq) → Cu(NO 3 ) 2 (aq) + 2 NO 2 (g) + 2 H 2 O (l) Oxidizing Half Reaction: Cu (s) → Cu 2+ (aq) + 2e - Reduction Half Reaction: 4 H + (aq) + 4e - + 2 NO 3 - (aq) → 2 NO 2 (g) + 2 H 2 O (l) Oxidizing Agent: Nitric Acid (HNO 3 ) Reduction Agent: Copper (Cu) Step 5 Redox Reaction: Balanced Chemical Equation: 3 CuSO 4 (aq) + 2 Al (s) → 3 Cu (s) + Al 2 (SO 4 ) 3 (aq) Oxidizing Half Reaction: 2 Al (s) → 2 Al 3+ (aq) + 6e - Reduction Half Reaction: 3 Cu 2+ (aq) + 6e - → 3 Cu (s) Oxidizing Agent: Copper Sulfate (CuSO 4 ) Reduction Agent: Aluminum (Al) Based on the balanced chemical equation for Reaction 5, the compounds being removed are copper sulfate (CuSO 4 ) and aluminum sulfate (Al 2 (SO 4 ) 3 ). Ethanol has a relatively low boiling point and evaporates quickly at room temperature. By rinsing the copper product with ethanol, residual water from previous washing steps can evaporate more effectively, aiding in drying. Ethanol is generally considered compatible with copper and does not react chemically with it under normal conditions. This ensures that the washing solvent does not introduce any additional contaminants or react with the copper product. 7 P. Sotelo SP2024

A steam bath was the chosen method to dry the copper product because it prevents the oxidation of the copper product by avoiding direct exposure to atmospheric oxygen. The percent recovery of the copper is 79.5%. The Law of Conservation of Mass is a fundamental principle in chemistry that states that in a chemical reaction, mass is neither created nor destroyed. The total mass of the reactants before a chemical reaction is equal to the total mass of products after the reaction. If the percent recovery is not 100%, it may be caused by an incomplete drying process. If residual water is left behind, it can lead to an overestimation of its mass during the weighing process. Another reason is the overheating of copper during the drying procedure. This can lead to the oxidation of the product through atmospheric oxygen. Percent Recovery: (0.287 g / 0.361 g) x 100% = 79.5% If the percent recovery is above 100%, it may be caused by the contamination of impurities in the final copper recovered which can lead to the overestimation of the final mass. Another reason is the loss of copper product during the various chemical reactions along the way. If the percent recovery is below 50%, it may be caused by an early completion of step 5. If the copper being recovered on the aluminum wire has not fully formed and was taken out too early, it will be a lower mass than the original copper wire. Another reason is the loss of product during the washing process. 8 P. Sotelo SP2024

REFERENCES 1. Cauwenbergh, Robin, and Shoubhik Das. “Photocatalysis: A Green Tool for Redox Reactions.” Synlett , Georg Thieme Verlag KG, 9 June 2022, www.thieme-connect.com/products/ejournals/abstract/10.1055/s-0040-1706042 . 2. Li, Shuwei, et al. “Anionic Redox Reaction and Structural Evolution of NI-Rich Layered Oxide Cathode Material.” Nano Energy , Elsevier, 4 May 2022, www.sciencedirect.com/science/article/abs/pii/S221128552200413X?via%3Dihub . 3. “Lavoisier.” Chemistry LibreTexts , Libretexts, 13 June 2023, chem.libretexts.org/Bookshelves/General_Chemistry/General_Chemistry_Supplement_( Eames)/Chemistry_Basics/Lavoisier. 4. Web Solutions LLC. “Oxidation-Reduction Reaction - History, Oxidation Numbers, Corrosion, Biological Processes, Current and Future Uses - Examples of Oxidation- Reduction Reactions.” History, Oxidation Numbers, Corrosion, Biological Processes, Current And Future Uses - Examples of Oxidation-Reduction Reactions - JRank Articles , 2023, science.jrank.org/pages/4964/Oxidation-Reduction-Reaction.html. 9 P. Sotelo SP2024

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