Question

Why does micelle formation take place when soap is added to water? Will a micelle be formed in other solvents like ethanol also?

Answer 1

Hint: We know that the formation of micelle takes place when soap is added to water because the hydrocarbon chains of soap molecules are hydrophobic(water repelling ) which are insoluble in water but the ionic ends of the soap are hydrophilic(water attracting) and hence soluble in water.

Complete step by step solution:
In a soap micelle ,the uncharged ends of the hydrocarbon chains are on the inside whereas the charged ionic ends are on the outside. A micelle will not be formed in other solvent such as ethanol because the hydrocarbon chains of soap molecules are soluble in organic solvents like ethanol. The molecules of soap are sodium or potassium salt of long chain carboxylic acids. At the one end (long non-polar end ) of the soap molecule is hydrocarbon chain insoluble in water but soluble in oil and at the other end (short polar end ) of the soap molecule ,there is a carboxylate ion, which is hydrophilic, i.e. water soluble but insoluble in oil. The short polar end with carboxylate ion turns the water away from dirt .The long non-polar end gravitates towards and surrounds the dirt and absorbs the dust in it. The soap molecule thus helps in dissolving the dirt in water and we can wash our clothes clean.

Note: In this problem we have seen the formation of micelle. A micelle is an aggregate of monomer surfactant molecules dispersed in a liquid colloid. For the formation of micelle it is important that the solvent should not be organic like ethanol because the hydrocarbon chains of soap molecules are soluble in organic solvents.