Question

Soap solution is colloidal in nature and remove the dust particles by which of the following processes?
(A) Emulsification
(B) Adsorption
(C) Stripping
(D) Distillation

Answer 1

Hint: The cleansing action of soap results from their ability to lower the surface tension of water, to emulsify oil or grease and to hold them in a suspension in water. This ability is due to the structure of soap molecules.

Complete step by step answer:
> Let us go through the mechanism of cleansing action of soap. That is:
The process of dispersing one immiscible liquid in another immiscible liquid is called emulsification. So, the soap solution mixes with the dust particles to form an emulsifier.
When soap is dissolved in water, its hydrophobic ends attach themselves to dirt and remove it from the cloth.
- First, the molecules of soap arrange themselves in micelle formation and trap the dirt at the centre of the cluster.
- These micelles remain suspended in water like particles in a colloidal solution.
- The various micelles present in water do not come together to form a precipitate as each micelle repels the other because of the ion-ion repulsion.
Thus, the dust particles remain trapped in micelles (which remain suspended) and are easily rinsed away with water.
 Hence, soap micelles remove dirt by dissolving it in water.
> Adsorption is a process which involves the accumulation of a substance in the surface of another surface.
So, Emulsification and absorption are the processes through which soap solution removes dust particles. Therefore, correct options are (A) and (B).

Note: Stripping is a physical separation process in which one or more components are removed from liquid using a vapour steam. Distillation is a process of separating two liquids having different boiling points. Therefore, these two options are not correct.