To Prepare Ferric Hydroxide [Fe(Oh)3] Sol

Colloidal solutions are heterogeneous. They are made up of two components: the dispersed phase or solute and the dispersion medium or solvent. In a colloidal solution, the dispersed phase and dispersion medium do not form a single phase, and hence small or large particles of the solute remain visible in the colloidal solution. There are various types of colloids, one of them being sols. Sols are a type of colloidal solution wherein the dispersed phase is a solid component, and the dispersion medium is liquid. Ferric hydroxide sol is a lyophobic sol wherein the ferric hydroxide is solvent-repelling since it shows a very low affinity towards the dispersed medium. Since water is the dispersed medium, it can also be said that ferric hydroxide sol is hydrophobic. Other examples of lyophobic sols are Aluminum hydroxide and arsenic sulfide.

Table of Contents

• Aim 

• Requirements 

• Theory 

• Methodology 

• Observations 

• Conclusion

• Precaution 

• Summary 

• Questions

Aim 

To prepare ferric hydroxide Fe(OH)3 sol

Requirements

Beaker(250ml), Glass, rod, filter paper, burner, wire-gauze, Conical flask, tripod stand, stand with clamp, dropper, 2% Ferric chloride solution, distilled water, etc.

Theory

Various metal hydroxides and metal sulfides form a lyophobic sol since they have a very affinity towards the dispersed medium in which they are made. Ferric hydroxide is one such type of lyophobic sol prepared indirectly through hydrolysis using Ferric chloride in boiling distilled water. The reaction for this is as follows-

\(FeCl3 + 3H2O \to Fe(OH)3 + 3HCl\)

Hydrolysis of ferric chloride leads to the formation of insoluble ferric hydroxide particles, which aggregate together, forming larger colloidal particles. The stability of various lyophobic sols is due to the charge present on the outer surface of the colloidal particles.

Procedure

i) Preparation of FeCl3

1. Weigh 2g of pure FeCl3 in a beaker.

2. Add 100 ml of Distilled water and dissolve all the FeCl3 into it.

3. 2% Ferric chloride solution is prepared.

ii) Preparation of Fe(OH)3

1. Take a 250ml conical flask and clean it using the process of steaming out.

2. Add distilled water to this flask, boil it over a burner, and use a wire gauze.

3. Take the 2% Ferric chloride solution and add it to the boiling water, drop-wise, using a dropper.

4.  Heat the above flask until a deep red or brown coloured solution of Ferric hydroxide is not obtained. Keep adding extra water when required, as water is lost due to evaporation.

5. Allow the contents of the solution to come at room temperature. The final ferric hydroxide Fe(OH)3 sol is prepared.

Observations

As the process of hydrolysis begins small colloidal particles of ferric hydroxide appear, and they slowly aggregate and form large colloidal sols. The solution obtained is deep red or brown in colour.

Result

A lyophobic colloidal sol of ferric hydroxide was prepared using the process of hydrolysis.

Precautions

1. Clean all apparatus before and after use.

2. Be careful while working near the burner.

3. Remove the HCl produced in the reaction by the dialysis process.

4. Add the ferric chloride solution dropwise into boiling water.

5. Wear all the other safety gear such as lab coat, gloves etc., while working in a laboratory.

Lab Manual Questions

1. By which method ferric hydroxide colloid is prepared?

Ans: Ferric Hydroxide is a colloidal solution which is prepared indirectly through the process of hydrolysis of Ferric chloride. Boiling water is used for this purpose, and the final product is insoluble ferric hydroxide particles.

2. Describe different types of colloidal solutions.

Ans: There are 4 types of colloidal sols-

• Sols- The dispersed medium is water and the dispersed phase is a solid.

• Emulsions-Both dispersed medium and dispersed phase are liquid.

• Foam- Here, the dispersed phase is gas, and the dispersed medium is solids or liquids.

• Aerosols- Here, the dispersed phase is solid or liquid, and the dispersed medium is gas.

3. Why does HCl have to be removed during the formation of ferric hydroxide?

Ans: As a by-product of the hydrolysis reaction (HCl), hydrochloric acid is formed. This HCl destabilises the colloidal sol and hence needs to be removed from the colloidal solution, or a stable solution will not be obtained.

4. What is the charge of Fe(OH)3 sol?

Ans: Fe(OH)3 sol particles formed after hydrolysis undergo a process of agglomeration and form large colloidal particles   Fe3+ ions are absorbed by the colloidal particles giving them a positive charge on their surface.

Viva Questions

1. Fe(OH)3 chemical name is?

Ans: Fe(OH)3  stands for ferric hydroxide. It is a deep red or brown colloidal solution.

2. What are the qualities of a true solution?

Ans: True solutions are –

• Homogenous i.e. the solute particles completely dissolved in the solvent and hence form a solution.

•  They are in a single phase 

•  They do not have any suspended particles. eg. NaCl in water.

3. What are the components of a solution?

Ans: A solution is made of solute and a solvent.

4. Which process is used for purifying the Fe(OH)3 Sol?

Ans: The dialysis process is used for purifying the Fe(OH)3 Sol. This is done by removing HCl generated post the reaction.

5. What is hydrolysis?

Ans: A chemical reaction which leads to the decomposition of reactants and water is known as hydrolysis. Water is used for the breakage of reactants and for forming the end products.

6. What is agglomeration?

Ans: Agglomeration is a process of combination of two or more particles to form a larger particle or a combination of particles to form a larger mass.

7. What is dialysis?

Ans: The process of separating ions or molecules from the colloidal solutions is known as dialysis. It happens through the process of diffusion.

8. What is lyophobic sol and lyophilic sol?

Ans: Sols in which solute particles have a weak affinity towards the dispersion medium are known as lyophobic sols. Sols in which solute particles have a strong affinity towards the dispersion medium are known as lyophilic sols.

9. How HCl is formed while preparing ferric hydroxide Fe(OH)3 sol?

Ans: During the hydrolysis reaction Fe3+ combines with the OH- of the water molecule forming the ferric hydroxide. The remaining H+ and Cl- ions combine and form HCl.

10. Give examples of foam types of colloidal solutions.

Ans: Examples of foam-type colloids are whipped cream, shaving cream, soap lather etc.

Practical Based Questions (MCQs) 

1. What is the ferric hydroxide formula?

1. Fe(OH)3

2. FeOH

3. Fe2OH2

4. FeOH2

Ans: Fe(OH)3

2. Lyophobic colloids can be prepared by

1. Boiling water 

2. Add the constituents slowly while constantly stirring

3. Take ice cold chilled water and then adding the constituents while stirring

4. Both A and B

Ans: Both A and B

3.______is a universal solvent

1. Alcohol

2. Glycerin

3. Water

4. Esters

Ans: Water

4. Hydro means______and Lysis means____

1. Water, Breakage

2. Breakage, Water

3. Liquid, Joining

4. Solvent, Reformation

Ans: Water, Breakage

5. State which of the following are true-

1. Ferric chloride is positive charged sol

2. Ferric hydroxide sol is positively charged

3. Starch sol is positively charged

4. Lyophobic are solvent loving

Ans: Ferric hydroxide sol is positively charged

6. One molecule of Fe(OH)3 requires_____and _____

1. FeCl3,H2O

2. 3H2O, FeCl3

3. 3FeCl3, 4H2O

4. 4H2O, 2FeCl3

Ans: 3H2O, FeCl3

7. What is by-product during the formation of Ferric hydroxide?

1. Sulfuric acid

2. Nitric acid

3. Hydrochloric acid

4. Sodium Hydroxide

Ans: Hydrochloric acid

8. HCl is a strong ___and can donate _____H+ ions

1. Acid, 1

2. Acid, 2

3. Base, 1

4. Weak acid, 1

Ans: Acid, 1

9. What is another name for ferric hydroxide?

1. Iron dihydrate

2. Ion trihydrate

3. Ferrous hydroxide

4. Iron hydroxide

Ans: Iron hydroxide

10. Find the odd man out

1. Margarine

2. Ice cream

3. Mayonnaise

4. Brine solution

Ans: Brine solution

Summary

In a colloidal solution the solute remains suspended in the solvent. Colloids are of various types depending on the dispersed phase and the dispersion medium used. Lyophobic Sols are a type of colloidal solution wherein the solid dispersed phase has less affinity towards the liquid dispersion medium. Ferric hydroxide is one such example of Lyophobic sols. It is prepared by hydrolysis of ferric chloride with boiling water. Ferric hydroxide is a dark red or brown coloured solution which has various applications in industries and chemical labs.