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HS CHEMISTRY Smelting Copper Contributed by Jessica Favela-Casillas BACKGROUND Copper is smelted starting from a copper ore, usually called Chalcopyrite, CuFeS 2. It is combined with limestone and sand to produce Iron Oxide, FeO, and leaves Copper Sulfide. The Copper Sulfide is then melted and burned to release another pollutant, Sulfur Dioxide, a pollutant that is linked to long-term health problems for those exposed to it. For every ton of copper produced at a refinery such as Asarco, 1.5 tons of slag and two tons of sulfur dioxide are produced and released into the atmosphere. Students explore the separation of copper from a compound through chemical means in a manner similar to that of a refinery or smelter and discover the impact of pollutants generated from the smelting and extracting. Introduction: Students examine the chart below and discuss implications for the waste products in the environment. Process materials inputs and pollution outputs for copper smelting and refining Process Material input Air emissions Process wastes Other wastes Copper Copper ore, Flotation Tailings containing concentration water, chemical wastewaters waste minerals reagents, such as limestone thickeners and quartz Copper leaching Copper Uncontrolled Heap leach waste concentrate, leachate sulfuric acid Copper smelting Copper Sulfur dioxide, Acid plant blow concentrate, particulate down siliceous flux matter slurry/sludge, slag containing containing iron arsenic, sulfides, silica antimony, cadmium, lead, mercury and zinc Copper Copper matte, Sulfur dioxide, Acid plant blow conversion scrap copper, particulate down siliceous flux matter slurry/sludge, slag containing containing iron arsenic, sulfides, silica antimony, cadmium, lead, mercury and zinc Electrolytic copper refining Blister copper, sulfuric acid Slimes containing impurities such as gold, silver, antimony, arsenic, bismuth, iron, lead, nickel, selenium, sulphur and zinc Discuss: Asarco smelted copper and other compounds for almost 100 years. How does the information in the chart make you feel about being so close to the Asarco smelter? What do you think was done with the waste? How do you use copper? Now that the smelter is closed, where is copper smelted today? EXPLAIN Asarco has smelted copper, and like many refineries, there is chemical waste left over that has harmed people and the environment. The following chemical reactions demonstrate the pollutants produced by refineries. Compare the reactants to the products. Identify each part of the equation identifying the metal being smelted, the compound it is being separated from and the waste. 1. 2. 3. 4. 5. 6. 7. 8. 9. 2 CuFeS2 + 3 O2 → 2 FeO + 2 CuS + 2 SO2 2 CuS + 3 O2 → 2 CuO + 2 SO2 2 FeS(l) + 3 O2 + 2 SiO2 (l) →2 FeSiO3(l) + 2 SO2(g) 2 FeS + 3 O2 → 2 FeO + 2 SO2 CuCO3 ------> CuO + CO2 2 Zns + 3 O2 2 ZnO + 2 SO2 2 SO2 + O2 2 SO3 ZnO + CO Zn (vapor) + CO2 List all the waste EXPLORE Purpose: You will perform a chemical experiment demonstrating a chemical reaction that separates a metal from a compound and determine what was is left over. Materials: Copper (II) chloride, one piece of aluminum foil (10 cm x 10 cm), 250 mL beaker, stirring rod, thermometer, distilled water, stopwatch, safety goggles, balance Procedure 1. Measure 3 grams of copper (II) chloride and make observations about its physical appearance. 2. Pour 100 mL of distilled water into the copper (II) chloride. Stir with the stirring rod. 3. Make an observation about the copper chloride dissolved in water. 4. Take the mass of your aluminum. Solid Copper (II) Chloride Copper (II) chloride dissolved in water Solid Aluminum 5. Lightly crumble the aluminum foil and place in the beaker. You can push it under the surface with the stirring rod. 6. Make as many observations as you can about the reaction in the beaker. Observation of reaction: What do you see happening? Color? What is Dissolving? What do you feel? Measuring Copper 1. With tongs, extract the chunk of “left over” aluminum. Allow all liquid to fall back into beaker. Take the mass of the aluminum. 2. Shape the Filter paper into a cone and filter the contents into an empty beaker scrape the Copper, Cu, off. Take its mass. Record. Mass of copper (II) chloride which reacted Mass of aluminum metal (initial) Mass of leftover aluminum wire (final) Mass of aluminum metal which reacted Mass of copper actually produced Initial – final Aluminum In this lab, copper (II) chloride reacts with aluminum metal in a single displacement reaction. Use the Data collected above. ALWAYS DO A “NEED” AND “GIVEN” TO SOLVE THESE PROBLEMS. 1. Write a balanced chemical equation for the single replacement reaction of copper (II) chloride with aluminum metal to produce copper metal and aluminum chloride. 1.a. Calculate the number of moles of copper (II) chloride used. 1. b. Calculate the number of moles of aluminum metal used. 2. Determine the limiting reactant. 3. What is the excess reactant? There are only two reactants: 4. How much excess reactant (in grams) is left over once the reaction is completed? Analysis: Looking at the access reactants, is excess reactant a larger quantity than the copper produced? What happened to the Aluminum and the Chloride that reacted? Write the chemical equation: What element was desired to be extracted? What waste was left over? In a smelter, if copper was extracted using these chemical means, what happens to the left over chemicals? What can you do to ensure that these are disposed properly? What tests can you conduct to insure that the land is safe for others to settle on a smelter site? Share the information you have learned about copper smelting with someone younger than you. What do they think about it? What can we do about it?