Aluminum Lab: The Purpose Of The Creation Of Alum

The purpose of the making alum from aluminum lab was to create alum from a series of chemical reactions involving aluminum. Small pieces of an aluminum can were cut and measured before being taken through a series of chemical reactions. This process involved filtering out waste product that was no longer needed in the reaction by using Whatman #4 filter paper and an aspirator. The first reaction that took place was placing aluminum pieces into the strong base NaOH and then heating it. This reaction is shown in the equation
〖2Al〗_((s))+〖2KOH〗_((aq))+〖6H〗_2 O_((l))→〖2K〗_((aq))^++〖2Al(OH)〗_(4(aq))^-+〖3H〗_(2(g)) (1). The solution was allowed to cool before being filtered. The filtrate was then mixed with
the strong acid H_2 〖SO〗_4 which cause two reactions to take place. The first reaction is shown in the equation
〖2Al(OH)〗_(4(aq))^-+H_2 〖SO〗_(4(aq))→〖2Al(OH)〗_(3(s))+〖2H2O〗_((aq))+〖SO〗_(4(aq))^(2-) (2).
The second reaction that took place was
〖2Al(OH)〗_(3(s))+〖3H〗_2 〖SO〗_(4(aq))→〖Al〗_2 〖(SO〗_4 )_(3(aq))+〖6H〗_2 O_((l)) (3).
As the solution was cooled, an alum precipitate began to form. This reaction can be seen in the equation
K_2 〖SO〗_(4(aq))+〖Al〗_2 〖(SO〗_4 )_(3(aq))+〖24H〗_2 O_((l))→〖2KAl(SO〗_4 )_2*〖12H〗_2 O_((s)) (4).
The solution was then cooled which caused the formation of alum crystals. This reaction is shown in the equation
K_((aq))^++〖Al〗_((aq))^(3+)+〖2SO〗_(4(aq))^(2-)+〖12H〗_2 O_((l))→〖KAl(SO〗_4 )_2*〖12H〗_2 O_((s)) (5).
A real world use of this laboratory experiment is through hydrometallurgy. Hydrometallurgy is the process of obtaining pure metals from ores. This process is incredibly is performed in a similar method in which an ore containing multiple metals is run through chemical reactions involving strong acids and bases in order to extract a particular type of metal. The process of making alum from aluminum is also important in the real world. Alum is a type of salt that is created in the form of crystals. Alum is an ingredient found in many products in pharmaceuticals, cosmetics, the food industry, as well as paper, dyes, glue and
explosives.
Procedure
A 5 x 5 cm piece of aluminum was stripped of its coating and cut into 2 x 2 mm pieces. The mass of the aluminum pieces was measured before adding 25 mL of 1.4 M KOH to the aluminum pieces making sure to stir well and slowly. The solution was warmed on a hot plate for 20 minutes. A glass funnel was placed on a ring stand where a Whatman #4 filter paper was folded and placed into the funnel before the entire funnel was placed in a beaker. After all of the aluminum reacted with the NaOH, the solution was allowed to cool before it was filtered. 10 mL of 9 M H_2 〖SO〗_4 which was mixed with the filtrate while being stirred. A beaker of ice was prepared and the filtrate was placed in the beaker in order to cooled for 20 minutes. The temperature was recorded once crystallization was complete. A Whatman #4 filter paper was placed in a Buchner funnel attached to an aspirator. The aspirator was turned on and the alum crystal were transferred using a rubber policeman. Two 10 mL portions of methanol were added in succession in order to wash the excess H_2 〖SO〗_4 out of the crystals. The aspirator was allowed to run for 10 minutes before the crystals were weighed.
Data
The data from Table 1 was gathered by weighing the mass of aluminum and then converting to the mass of alum using stoichiometry. The table contains data for the mass of aluminum, moles of aluminum, theoretical moles of alum, molar mass of alum, theoretical yield of alum, experimental yield of alum, and the percentage yield of alum.