Chem lab #3

Chem lab #3
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Recycling Aluminum By Yiliu (Peter) Wang Teaching Assistant: Josie Bodle October 12 th , 2007
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Results and Discussion: Recycling Aluminum: Aluminum was recycled (in a general sense of adapting to a new use), or converted, to alum. Alum is a name for a class of compounds with the general formula of MM’(SO 4 ) 2 , where M is a nonvalent cation such as K + , and M’ is a trivalent cation such as Al +3 . In this experiment, alum is specifically sulfate dodecahydrate [KAl(SO 4 ) 2 – H 2 O]. In this experiment, there were intermediary chemical reactions that were needed to convert aluminum into alum. The net reaction is given by the reaction: 2Al(s) + 2KOH(aq) + 4H 2 SO 4 (aq) + 22H 2 O -> [2KAl(SO 4 ) 2 - 12H 2 O](s) + 3H 2 (g) In order to scale the experiment down so as to prepare a theoretical product yield of 23 grams of alum, the limiting reagent of all reactants – Al, KOH, H 2 SO 4 - was first calculated to be aluminum, which was .444 moles. Then using mole ratios through the net reaction and by conversion factors, 1.31 grams of Al was calculated to yield 23 grams of Alum. The conversion ratio of all reactants, thus, was 12 g Al (given in procedure) over 1.31 = 9.2. All reactants, then, were converted down to: .065 L 1.4 Molar KOH .026 L 9.0 Molar H 2 SO 4 .0065 L H 2 SO 4 aliquot (counted in the original .026 L H 2 SO 4 solution) .0065 L H 2 O for rinsing residue in gravity filtration system .033 L 50/50 ethanol solution Week 1 Experiment: 1. Aluminum, from a SoBe Essential Energy Berry Pomegranate can, was cut into roughly five squares that weighed a total of 1.308 grams. It was then placed into a 600 mL beaker with 065 L 1.4 Molar KOH solution in the fume hood. Then, it was heated on a hot plate, and all the gas that was observed to rise from the chemical reaction, and not from the boiling water, was depleted
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after the 22:00 minute mark. Around 2/3 of the original water was lost, so 1/3, or 20.0 mL of water was put into the solution afterwards. Observations of chemical reaction on hotplate: the reaction became
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