Lab report 1 - 90 o C +90 o C = 90 o C 2 Average ending...

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Results and Discussion: In this experiment, alum [KAl(SO 4 ) 2 ∙12H 2 O] was synthesized from aluminum. The theoretical yield of the experiment was 23 g. A sample of 1.313 g of aluminum was reacted with 65.5 mL of 1.4 M KOH. The reaction used was 2Al (s) + 2KOH (aq) + 6H 2 O (l) → 2K + (aq) + 2Al(OH) 4 - + 3H 2(g) The Al(OH) 4 - was then mixed with 6.6 mL of 9 M H 2 SO 4 . Al(OH) 4(aq) + H + (aq) → Al(OH) 3(s) + H 2 O (l) An additional 19.4 mL of the 9 M H 2 SO 4 was then added to the aluminum hydroxide. Al(OH) 3(s) + 3H + (aq) → Al 3+ (aq) + 3H 2 O (l) As the solution is cooled, the following reaction ensues: K + (aq) + Al 3+ (aq) + 2SO 4 2- (aq) 12H 2 O (l) → KAl(SO 4 ) 2 ∙12H 2 O (s) The mass of the weighing boat and filter paper was 7.996 g. The mass of the weighing boat, filter paper, and alum sample was 17.827 g. The mass of the alum obtained was: 17.827- 7.996= 9.83 g. The percent yield of the alum was: 9.83 g x 100 = 42.7% 23 g. Table 1: Melting Point of Alum Data and Results Trial Starting Melting Temperature (C 0 ) Ending Melting Temperature (C 0 ) Melting Range (C 0 ) 1 90 92 2 2 90 92 2 Average starting melting temperature:
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Unformatted text preview: 90 o C +90 o C = 90 o C 2 Average ending melting temperature: 92 C + 92 C = 92 C 2 Average melting temperature of the alum: 90 o C + 92 C = 91 C 2 Average melting range: 2 C + 2 C = 2 C 2 % error = 92.5 C- 91 C x 100 = 1.62% The results are accurate. 92.5 C Conclusion: There was not a very high percent yield of the alum in this experiment. The yield was not small, but was not very good either. Error could have resulted from certain areas of the experiment where the entire solution was not used or reacted. For example, after the aluminum was reacted with KOH and the solution was filtered, all of the solution may not have been transferred through the filter paper. Also, some reactions may not have been allowed to go to completion. However, the sample of alum produced was very pure. There was not a large melting range and the average melting temperature was accurate....
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This note was uploaded on 04/07/2008 for the course CHEM 1560 taught by Professor Baird, b during the Fall '07 term at Cornell University (Engineering School).

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Lab report 1 - 90 o C +90 o C = 90 o C 2 Average ending...

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