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  • Published on: 15th October 2019
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Pre-lab:

1. Sodium Hydroxide (NaOH) is another example of another a caustic solution. Caustic solutions can be extremely harmful if they come into contact with skin.  The best way to safely handle these solutions with goggles and gloves

2. Nucleotides are a good example of covalent bonds between phosphate groups in the human body observations like this show how interconnected biology and chemistry are.

3.  Crystallization is the purification of solids where synthesis is combining two substances to form a more advanced solution.

Lab Report 6 Synthesis of Aluminum

Introduction:

This experiment required us to use synthesis to create advanced compounds from the materials. In order to understand the process and purpose of this lab it is necessary to have a general understanding of synthetic chemistry itself. Synthetic chemistry is finding different ways to create various forms of matter. Synthetic chemistry is very important in pharmaceuticals, energy efficiency, and understanding various biological systems. By advancing our research in synthetic chemistry we could increase production of the things that support our life styles.  This lab required careful measurement of various chemicals that would be needed to change the state of aluminum. We measured the mass throughout the experiment to see how and what was changed.

Methods:

We used numerous caustic and potentially dangerous solutions in the experiment so it was very important to use gloves and goggles. For this experiment we used a Buchner funnel to help filter the various solutions. We obtained a piece of aluminum foil and recorded its mass. After the mass was recorded we ripped the foil into small pieces and placed the pieces into a 250mL beaker. We then proceeded to obtain 25mL of Potassium Hydroxide to dissolve the aluminum in. Using a graduated cylinder, we proceeded to pour 5mL at a time of the potassium hydroxide into the 250mL beaker to dissolve the aluminum. The reaction took a few minutes to get started but the aluminum all dissolved relatively quickly. We could tell that a chemical reaction was taking place due to the fizzing and temperature change.  After the aluminum was completely dissolved we proceeded to filter it using the Buchner funnel. This process involved wetting filter paper with deionized water and pouring the aluminum potassium hydroxide solution through. We filtered the solution and placed it back into the beaker. We made sure to clean the funnel so we could use it filter more solutions. We used a graduated cylinder to measure 35mL of sulfuric acid. We added the sulfuric acid to the solution we obtained earlier and recorded the reactions. A white gel like precipitate was formed initially but after additional sulfuric acid was added the precipitate began to break down and dissolve.  After this step we used a hotplate to decrease the volume of the solution. We added two boiling chips and kept the hotplate at 400 degrees Celsius. We kept the beaker on the hotplate until the volume of the solution had been reduced to 40 mL. After the volume had been reduced we placed it on a wire grid to cool. We placed the beaker into an ice bath and waited for the crystals to form. We collected the aluminum crystals and filtered them using the funnel. We washed the crystals in ethanol solution and broke them down using a glass stirring rod. After the crystals were broken down we placed them in a beaker and set them in the oven for twenty minutes. After twenty minutes had passed we recorded the mass of the beaker with dried alum. In order to have accurate measurements of the crystals we first found the mass of a clean beaker and subtracted that from the mass of the beaker with crystals to get an accurate measurement of the mass of the crystals.

Analysis:

Below is a table which represents the different processes the aluminum went through.

Started with

added

reactions

Final product

Aluminum foil (0.95) g

Potassium Hydroxide (KOH) 25mL

The aluminum fizzed and dissolved slowly initially and the temperature increased  

Aluminum Potassium Hydroxide 2KAl(OH)4

Aluminum Potassium Hydroxide 2KAl(OH)4

Sulfuric acid H2SO4 35mL

Initially a clear, cloudy, and jelly type of precipitate was formed but after more sulfuric acid was added the precipitate dissolved

Heated at 400 degrees Celsius

The volume was decreased to 40mL

40 mL’s

40 mL’s of

Putting the solution on an ice bath

Crystals of aluminum were formed and began to separate from the solution

Aluminum crystals

Aluminum crystals

Washed with 50mL of ethanol

N.A.

119.409g of Aluminum crystals +

119.409g of Aluminum crystals

Placed in the lab oven for 20 minutes

Mass decreased

116.269g of aluminum crystals

The next table has our results for the theoretical and percent yield equations as well as the data from two neighboring groups.

Group #

Initial mass of Aluminum (g)

Final mass of the aluminum crystal (g)

Theoretical yield (g)

Percent yield (%)

Percent Difference (%)

Group 1 (my group)

0.95

10.63

14.87483473

53.5693120

N.A.

Group 2

1.02

13.45

16.96753411

77.6597900

22.556778

Group 3

1.26

12.06

18.34829011

41.2244565

42.657892

Throughout this experiment numerous chemical reactions took place for different synthesis. The ionic equations are listed below

1. 2Al(s) + 2KOH(aq) + 6H2O(l) →2KAl(OH)4(aq) + 3H2(g)

2. 2KAl(OH)4(aq) + H2SO4(aq) →2Al(OH)3(s) + K2SO4(aq) + 2H2O(l)

3. 2Al(OH)3(s) + H2SO4(aq) → Al2(SO4)3(aq) + 6H2O(l)

4. K2SO4(aq) + Al2(SO4)3(aq) + 24H2O(l) →2KAl(SO4)2 ⋅12H2O(s)

Numerous times throughout this experiment we would unintentionally use the wrong amount of the solutions, take things off of the heater too soon or too early, and do the calculations incorrectly. These small things can quickly add up and make your data less valuable. In a multi step experiment like this one it is very easy to make mistakes.  The difference between synthesis and crystallization was easy to see. We used synthesis to form the various solutions and crystallization processes to form the crystals. Below is the molecular reaction with sulfuric acid hand drawn

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