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UCM CHEM 002-01 - lab report 6

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Dolores RamirezExperiment #6 – Chemical Recycling: Synthesis of Alum from AluminumDolores RamirezChem 2 Lab 2LoganApril 1, 2013Experiment #6 – Chemical Recycling: Synthesis of Alumfrom Aluminum1. Introduction: The purpose of this lab is to adapt and scale a procedure for the synthesis of alum,KAL(SO4)2∙12H2O. Then to successfully analyze the percent yield based upon limiting reagent calculations; and represent the synthesis of alum as the sum of three consecutive reactions.1) Experimental:a) Materials:i. Chemicals: 1.4 M KOH; 9 M H2SO4 ; acetone; NaHCO3(s)b) Apparatus:i. Aluminum beverage can or foil; sturdy scissors or tin snips; coarse steel wool or metal pot scrubber; crushed ice; short stemmed glass filter funnel; Whatman No. 4 filter paper; filter flask; Buchner filter funnel; filter paper to fit Buchner funnel; aspirator apparatus or House vacuum; hot plate; rubber policeman; melting point capillary tubes; melting point apparatus; 25 mL and 50-100 mL graduated cylinders; 150 to 250 mL beakers (3).c) Procedure: 1. Before lab calculate the scaling factor and get it checked my instructor2. Begin cutting up pieces of aluminum in ( about 0.5 X 0.5) size squarespieces3. In a beaker add 12 g of the small pieces of aluminum and record the mass to the nearest milligram. Then obtain 350 mL of 2 M KOH solution.4. Carefully add the KOH to the beaker with the pieces of aluminum witha small rod, then warm the solution on a hot plate for 20 min with occasional stirring.5. While solution is warming set up a short stemmed glass funnel using a ring stand and iron ring or funnel support. Place the stem of the funnel in another clean beaker. Fold a peace of filler paper in to quarters and place it in the funnel. 6. Place a piece of funnel paper into the funnel that it will keep it in place, get rid of any excess water7. .) After the Aluminum has all completely dissolved pour the substance into the funnel making sure not to over flow the funnel. Use the stirring rod to guide the solution, the filtrate should be colorless.18. Obtain 180 mL of 10 M H2SO4 then add to the beaker rapidly. Stir the solution thoroughly and let the beaker with the filtrate to cool. 9. Fill another beaker half full with water and crushed ice then place the beaker containing the alum solution into the ice bath for about 20 minutes and stir occasionally until the solution inside is at 5oC.10. Place a piece of filter paper in the Buchner funnel and turn on the aspirator, then add the solution that is at 5 degrees Celsius into the funnel. Remove all the crystals by using a rubber policeman to scrape out and loosen the crystals.11. Neutralize the sample in the Buchner funnel by checking the pH range between 6 - 8 then add solid NaHCO3 to the solution and wait until bubbling ceases and then dispose after TA approval. 12. Add roughly about 28-30 mL of acetone to the solution in the Buchner funnel, the substance will be ready to remove once the smell of the acetone has faded and is no longer present. Make sure to break the seal on the collar of the Buchner funnel and shut off the vacuum.13. Transfer the dried alum crystals to the massed beaker. Use the rubber policeman to scrape the crystals stuck to the filter paper then reweigh the mas of Alum obtained. 14. Clean up and dispose of chemicals as directed.3) Results and Discussion:During this experiment we were able to obtain and measure masses. The masses include: 0.853 g Al, 10.058g of synthesized Alum, 14.21 mL of H2SO4, 35.54 mL of KOH 15g. Alum was the theoretical and 10.058g of Alum was the experimental. While observing the experiment we saw the dissolved aluminum solution being poured into the funnel on the iron ring, the funnel collected blackish-grey residue while the funnel cleaned the solution allowing it to seep through as a clear and colorless solution. The visible changes when the sulfuric acid inside the Potassium Hydroxide was added quicklyinto the beaker forming a cloudy, smoky, white substance as it evaporated. When the beaker was added into the ice bath the temperature quickly fell when crushed ice was added to make the temperature drop 5oC. Within the first few minutes the temperature had gone from 20 oC to 11oC. As the NaHCO3 was added to the sample in the Buchner funnel the substance inside the beaker bubbled for roughly 15 seconds until the substancehad reached a neutral 6-8 level on the pH scale-allowing disposal.4) Conclusion:As conclusion this experiment was successful in synthesizing the Alum from the Aluminum. This experiment allowed us to understand and visualize the three differentreactions during the synthesis of the Alum. This lab experiment also allowed us to understand the process by which the Aluminum is dissolved or broken down and then converted or synthesized back into a solution. Ultimately this lab was successful in both the synthesis and the recycling process of the Alum and Aluminum.a) Initialed Duplicate Laboratory Notebook Page(s):i. The initialed duplicate laboratory notebook page(s) must be included after your conclusion upon report submission.25) Report Questions:1. For the following answers refer to page 4 for the calculationsa. The experimental scaling factor that gave rise to the 15g theoretical yield I 14.07gb. The correct volume for KOH is 35.54mL KOH and the correct volume of H2SO4 is 14.21 mL H2SO4.c. The theoretical yield of the alum is 15.00g Alum2. The experimental yield of the product is 7.229 g of alum and the overall percent yield for the alum is 48.19% yield (refer to page 5 for the calculations).3. Refer to page 5 for the


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