Lab 18 - qualitatively analyzed First alum crystals were...

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In part one of this experiment alum was synthesized from aluminum foil. First .501g of aluminum foil was added then 25ml of 4M KOH and the aluminum was dissolved. Then 20ml of 9M H 2 SO 4 was added and the solution heated to evaporate excess liquid. Crystals were allowed to form and they were washed with 50% ethanol in water then dried. The final weight of the crystals was 15.431g or .0186 mols alum. The theoretical yield for this experiment was 8.82g so the percent yield was 136.1%. This extra mass was due to water not having been completely evaporated away. Some sources of error could have been from not having evaporated away all the water or filtering the solution which could have added mass. Equation used was 2Al(s)+2KOH+22H 2 O+4H 2 SO 4 >2KAL(SO 4 ) 2 *12H 2 O(s)+3H 2 (g) In part two of this experiment the composition of alum was
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Unformatted text preview: qualitatively analyzed. First alum crystals were added to water in two small test tubes. In one test tube a few drops of BaCl 2 were added and white crystals formed at the top and the solution became thick and crystallized. In the other test tube a few drops of .1M KOH were added and the top of the solution became a little cloudy. A flame test was also used in this part. The KCl solution made the flame turn purple as did the alum solution. This part tested for Al 3+ , SO 4 2-, K + , and H 2 O. Sources of error could have been if the alum synthesized from part one was not done correctly. In conclusion this experiment worked out very well. Alum was synthesized in the first part and then analyzed in the second. All results were acceptable....
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Lab 18 - qualitatively analyzed First alum crystals were...

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