ll. Procedure 1. Obtain about 0.5 grams of aluminum (shredded foil or granules) in a beaker. Record the exact mass as me

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Ll Procedure 1 Obtain About 0 5 Grams Of Aluminum Shredded Foil Or Granules In A Beaker Record The Exact Mass As Me 1 (71.27 KiB) Viewed 75 times

ll. Procedure 1. Obtain about 0.5 grams of aluminum (shredded foil or granules) in a beaker. Record the exact mass as measured by difference or taring on the electronic balance. 2. While wearing nitrile gloves, obtain 25 mL of 20% KOH WARNING: HIGHLY CAUSTIC.CLEAN UP ALL SPILLS IMMEDIATELY AND CAREFULLY. Under the hood, add this to the aluminum in the 250 ml beaker. Avoid breathing fumes as reaction progresses. While the hydrogen produced is benign, a plastic coating on foil may react to give toxic gases and oxide particulates that may cause lung irritation) 3. Allow the mixture to continue to react under the hood. All the shiny aluminum disappears when the reaction finishes. Black flecks and/or clear solution remain. Cool until the beaker can be touched. 4 Assemble apparatus for filtering: use a ring stand, a three fingered clamp, a Buchner funnel, a side arm flask (filtration flask), and a piece of tubing. Clamp the flask in place. Then add the Buchner funnel. Connect to a vacuum line with the tubing. See Figure 1. Figure 1. Set up for Buchner funnel. 5. Put a piece of filter paper in the Büchner funnel and pour the liquid mixture into the funnel. 6. From the flask, transfer the solution to a 50 ml beaker. SAVE THE SOLUTION; discard the filter paper with the black solid in the trash. 7. Cool another five minutes. With stirring, slowly add 15 ml of 6 M sulfuric acid. 8. Heat the mixture on low for about ten minutes with occasional stirring with a glass rod. 9. Cool to room temperature on the counter; while cooling create an ice bath using a 250 ml beaker about 20% filled with ice and a little water to make it a bit slushy: place the beaker with the solution in the ice bath for 10-15 minutes. Make sure the ice-water bath does not drown the beaker. 10. While waiting for the cooling, weigh an evaporating dish in which the alum will be collected at the end. 11. If no precipitate is present, scratch slowly up and down in a diagonal pattern on the side of the beaker with the alum solution with a stir stick. Another option is to add a pinch of alum (made by others in the past) to initiate the precipitation. Wait five additional minutes for the rest of the solid to precipitate. (This is called "seeding crystals.") 12. Filter with the Büchner funnel as before, only this time, keep the solid-the alum. Transfer solid to the evaporating dish either from the filter paper or scraped directly from the filter flask if they did not all get to the filter paper. Discard the solution as directed. Allow the alum crystals to dry and then weigh. 13. Weigh, calculate percent yield, and discard alum in provided container. Unplug the hot plate, grasping it by the plug. NOT the cord. CHEM 121 Adventures in General Chemistry I: Laboratory Exercises & Experiments Fall 2019 Page 41