Chapter 8, Problem 142A

Interpretation Introduction

Interpretation:

The chemical composition of a detergent is to be stated. The explanation as to how detergent removes oil and grease from fabric is to be stated.

Concept introduction:

The process via which soaps and detergents remove the dust particles (dust, grease, oil, etc) from the cloths or any other surface is termed as a cleaning process.

Answer to Problem 142A

The chemical composition of detergent is builders, surfactants, bleaches, enzymes, and other ingredients like optical brighteners, softeners, colorants, etc. The polar part of the detergent attracts with water and the non-polar part attracts with dust particles. After scrubbing, dust particles pull away from the clothes.

Explanation of Solution

Commonly the laundry detergent is used to wash clothes. The laundry detergent is composed of the following chemicals:

1. Surfactants: Surfactants reduce the surface tension of water so that water can wet the cloth very well. Surfactant absorbs into dust particles, forms an emulsion with water to clean dust. Therefore, surfactants are accountable for cleaning. Alkylbenzene sulfonates are one of the most common surfactant.

2. Builders: It is known that some metal (Ca and Mg) carbonate and bicarbonate present in water as a mineral. These metal ions can react with surfactant scum which makes the detergent less effective. Builders act as a chelating agent that removes these metal (Ca and Mg) carbonate and bicarbonate minerals via chelation and precipitation. Zeolites, polycarboxylates, silicates, citrates, etc are the most common builders.

3. Bleaches: As the name indicates bleach is used to remove color dust. Common bleach is sodium perborate, sodium percarbonate, etc. These bleaches are inactive in solid-state but become active when contact with water.

4. Other ingredients: The other ingredients are optical brighteners, softeners, colorants, etc. Perfume is also used in today’s detergent.

Cleaning Action of Detergents: The detergent dissociates into cations and anions. For example, the ionization of detergent sodium alkyl sulfate is shown below.

The alkyl part of the detergent anion is hydrophobic in nature which is attracted by dust particles. The sulfate part of the detergent anion is hydrophilic in nature which is attracted by water. Therefore, the detergent anion forms micelle with water. After scrubbing, dust particles pull away from the clothes.

Conclusion

The chemical composition of detergent is builders, surfactants, bleaches, enzymes, and other ingredients like optical brighteners, softeners, colorants, etc. The polar part of the detergent attracts with water and the nonpolar part attracts with dust particles. After scrubbing, dust particles pull away from the clothes.