Name: Uses of Adsorption
Uploaded: 2019-07-19
Duration: 2 min 48 s
Description: Do you know how gas masks work? How does a perfume scent stick to us for long hours? It's all possible due to adsorption. Isn't it interesting? Learn more.

Question

What are micelles? Discuss the mechanism of micelle formation and cleaning action of soap.

Accepted Answer

Micelles are the cluster or aggregated particles formed by association of colloids in solution. The formation of micelles take place above certain concentration called critical micelle concentration (CMC). For example, CMC for soaps is $10^{- 4}$ to $10^{- 3} mol L^{- 1}$ .

Mechanism of Micelle Formation:
Micelle are generally formed by the aggregation of several ions or molecules with lyophobic as well as lyophilic parts. These molecules or ions are called surface-active molecules. For example in soap sodium stearate the stearate ions associate to form ionic micelles of colloidal size. It has long hydrocarbon part of $C_{17} H_{35} -$ radical which is lyophobic end and ${COO}^{-}$ part which is lyophilic.

The dirt is held on the surface of clothes by the oil or grease which is present there. Since oil or grease are not soluble in water, therefore the dirt particles cannot be removed by simply washing the clothes with water. When soap is applied, the non-polar alkyl group dissolves in oil droplets while the polar groups remain dissolved in water. In this way each oil droplet is surrounded by negative charge. This negatively charged oil droplets cannot coalesce and a stable emulsion is formed. These oil droplets (containing dirt particles) can be washed away with water along with dirt particles.

What are micelles? Discuss the mechanism of micelle formation and cleaning action of soap.

Important Questions on Surface Chemistry

Learn and Prepare for any exam you want !