Chemistry lab Preparation of an Alum

Chemistry_lab_Preparation of an Alum

Academic year: 2020/2021

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Preparation of an Alum To Become more familiar with redox reactions. Practice mass and volume measurement techniques. To calculate the theoretical yield and percent yield of a synthesis reaction. IntroductionAlum is actually the name for a class of double salts of univalent and trivalent metals. aluminum foil, balance, beaker, wire gauze, filter paper, blue litmus, H2SO4, Buchner funnel, filter flask, water. Procedure1. First I weigh about 1 g of Al foil on a balance to at least two decimal places. 2. Place the weighed foil in a clean, dry 400 mL beaker and add 35 mL of water and 15 mL of KOH. 3. Place the beaker on the wire gauze and heat cautiously. Continue heating until all the aluminum metal has dissolved. 4. Cool the beaker and its contents to room temperature. Then filter the solution through filter paper. 5. Add a strip of blue litmus paper to the filtered solution. The litmus turns red in color. Add H2SO4 and continue heating. 6. Retrieve the litmus paper from the solution and cool the solution in an ice 7. Then I set up a vacuum filtration system. Place a piece of filter paper into the Buchner funnel. 8. When the alum precipitated I pour it in small portions onto the Buchner funnel. 9. Gently remove the filter paper together with the crystals from the funnel and place it on a large piece of filter paper. Dry the crystals and filter paper under a heat lamp. 10. Carefully transfer the dry alum from the filter paper onto the weighed weighing paper, weigh the alum and weighing paper together. 11. Calculate the theoretical yield of alum. Data and resultsWeight of aluminum foilWeighing paper alumWeighing paperWeight of alumNumber of moles of AlTheoretical yieldMolecular weight 1 g 5 g 0 4 0 mols 0 mols 6 The amount of aluminum foil used to perform this experiment was 1 g, and this mass was used to calculate the theoretical yield. The reason the percent yield was under could be due to the fact that some of the reactants did not react, instead, it just stayed in its original form. Also, some of the products may have been lost when transferred from one container to another. Potassium hydroxide is a strong base. It is extremely corrosive and will burn skin. Solutions of it, if splashed into the eye, can do irreparable damage so quickly that it is not possible to reach the eyewash fountain in time to prevent it. We must wear goggles throughout this experiment. Hydrogen gas is given off when aluminum metal is reacted with potassium hydroxide solutions. Hydrogen is extremely flammable. After rubbing aluminum can become shiny like silver color. After adding KOH to 250 mL beaker containing aluminum chips, it starts bubbling. After placing on a hot plate it starts bubbling vigorously and the KOH solution turns grey in color. Conclusion: In this experiment, Preparation of Alum from Aluminum Metal, was used to separate and extract alum from the paint and plastic materials present in aluminum foil. The experiment used potassium hydroxide and sulfuric acid to extract the alum. The experiment was

Preparation of an Alum

Objective- To Become more familiar with single-replacement redox reactions.

Practice mass and volume measurement techniques. To calculate the theoretical yield and percent

yield of a synthesis reaction.

Introduction-

Alum is actually the name for a class of double salts of univalent and trivalent metals.

Materials- aluminum foil, top-loading balance, beaker, wire gauze, filter paper, blue litmus,

H2SO4, Buchner funnel, filter flask, water.

Procedure-

1. First I weigh about 1 g of Al foil on a top-loading balance to at least two decimal places.

2. Place the weighed foil in a clean, dry 400 mL beaker and add 35 mL of water and 15 mL

of KOH.

3. Place the beaker on the wire gauze and heat cautiously. Continue heating until all the

aluminum metal has dissolved.

4. Cool the beaker and its contents to room temperature. Then filter the solution through

filter paper.

5. Add a strip of blue litmus paper to the filtered solution. The litmus turns red in color. Add

H2SO4 and continue heating.

6. Retrieve the litmus paper from the solution and cool the solution in an ice -bath.

7. Then I set up a vacuum filtration system. Place a piece of filter paper into the Buchner

funnel.

8. When the alum precipitated I pour it in small portions onto the Buchner funnel.

9. Gently remove the filter paper together with the crystals from the funnel and place it on a

large piece of filter paper. Dry the crystals and filter paper under a heat lamp.

10. Carefully transfer the dry alum from the filter paper onto the weighed weighing paper,

weigh the alum and weighing paper together.

11. Calculate the theoretical yield of alum.

Principles Of Chemistry I (CHEM 108)

York College CUNY

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