Preparation of Lyophobic Sol - Aluminium Hydroxide Sol

In this article, we have discussed a step-by-step procedure to perform an experiment to prepare Aluminium hydroxide sol. Carefully read the content on this page to understand the aim, procedure and materials required to perform the experiment. Try to perform the experiment and match your result with this.

Aim:

To prepare Aluminium hydroxide sol.

Theory:

Aluminium hydroxide can form a lyophobic sol. It is hydrophobic in nature and is obtained by hydrolysis of Aluminium chloride. The chemical equation for the same is shown as:

AlCl₃ + 3H₂O → Al(OH)₃ + 3HCl

The hydrochloric acid formed as a result of hydrolysis of AlCl₃ is removed by the method of dialysis as Al(OH)₃ sol gets affected in case of ionic impurities.

Materials required:

The apparatus and materials required for this experiment are as follows:

1. Glass rod
2. Round bottom flask
3. Boiling tube
4. Conical flask of 250 mL volume
5. Tripod stand
6. Funnel
7. Beaker of 250 mL volume
8. Burette
9. Wire gauze
10. Dropper
11. Burner
12. Wire gauze
13. Iron stand with clamp
14. Boiling tube
15. Distilled water
16. Solution of Aluminium chloride

Procedure

1. Prepare a 2% solution of Aluminium chloride by taking 2 g of pure Aluminium chloride in 100mL of distilled water.
2. Take the conical flask cleaned by a steaming out process with 100mL of distilled water.
3. With the help of wire gauze, boil the water.
4. Pour 10 mL of Aluminium chloride solution with the help of a burette or dropper.
5. Constantly keep stirring the boiling water mixture while adding Aluminium chloride solution.
6. Heat the conical flask containing a mixture until you see a white-coloured Aluminium hydroxide solution.
7. Allow the mixture to cool at room temperature.
8. Label the flask containing the mixture as Aluminium hydroxide sol.

Precautions to be taken during the experiment:

• Al(OH)₃ sol is affected due to the presence of impurities. Therefore to avoid this the conical flask is cleaned by steaming out process.
• The AlCl₃ solution is added dropwise.
• Heat the mixture of distilled water and Aluminium chloride solution until brown or deep red colour is obtained.
• The hydrochloric acid (HCl) formed is removed by the process of dialysis to avoid destabilisation of sol.

Viva Voce:

1. How to prepare 2% Aluminium chloride solution?

Ans: Mix 2 g of Aluminium chloride in 100 mL of distilled water.

2. Why is it important to clean the apparatus by steaming out the process?

Ans: Aluminium hydroxide sol gets affected due to the presence of ionic impurities. Therefore the apparatus is steam cleaned before performing the experiment.

3. Boil the mixture of Aluminium chloride solution and distilled water until it attains _______ colour.

Ans: White colour.

4. Hydrolysis of Aluminium chloride results in ________.

Ans: Hydrochloric acid.

5. What is the quantity of Aluminium chloride solution added to 100 mL distilled water?

Ans: 10 mL.