An associated colloidal system behaves as normal solution at low concentration but becomes colloidal at higher concentrations micelle formation happens because?
An associated colloidal system behaves as normal solution at low concentration but becomes colloidal at higher concentrations micelle formation happens because?
The correct option is D Above CMC and above Kraft temperature
Associated colloids are substances which at low concentrations behave as normal strong electrolytes, but at higher concentrations exhibit colloidal behaviour due to the formation of aggregates. The aggregated particles formed are called micelles.
The formation of micelles takes place only above a particular temperature called Kraft temperature and above a particular concentration called critical micelle concentration.
Let us take the example of soap solutions. Soap is sodium or potassium salt of a higher fatty acid. When dissolved in water, it dissociates into RCOO−andNa+ ions. The RCOO− ions, however, consist of two parts — a long hydrocarbon chain R (also called non-polar ‘tail’) which is hydrophobic(water-repelling), and a polar group COO–(also called polar-ionic ‘head’), which is hydrophilic (water loving). The RCOO− ions are, therefore, present on the surface with their COO− groups in water and the hydrocarbon chains R staying away from it and remaining at the surface. But at critical micelle concentration, the anions are pulled into the bulk of the solution and aggregate to form a spherical shape with their hydrocarbon chains pointing towards the centre of the sphere with COO− part remaining outward on the surface of the sphere. An aggregate thus formed is known as ‘ionic micelle’.
Hence, Soaps and synthetic detergents belong to the class of associated colloids.
The correct option is D Above CMC and above Kraft temperature
Associated colloids are substances which at low concentrations behave as normal strong electrolytes, but at higher concentrations exhibit colloidal behaviour due to the formation of aggregates. The aggregated particles formed are called micelles.
The formation of micelles takes place only above a particular temperature called Kraft temperature and above a particular concentration called critical micelle concentration.
Let us take the example of soap solutions. Soap is sodium or potassium salt of a higher fatty acid. When dissolved in water, it dissociates into RCOO−andNa+ ions. The RCOO− ions, however, consist of two parts — a long hydrocarbon chain R (also called non-polar ‘tail’) which is hydrophobic(water-repelling), and a polar group COO–(also called polar-ionic ‘head’), which is hydrophilic (water loving). The RCOO− ions are, therefore, present on the surface with their COO− groups in water and the hydrocarbon chains R staying away from it and remaining at the surface. But at critical micelle concentration, the anions are pulled into the bulk of the solution and aggregate to form a spherical shape with their hydrocarbon chains pointing towards the centre of the sphere with COO− part remaining outward on the surface of the sphere. An aggregate thus formed is known as ‘ionic micelle’.
Hence, Soaps and synthetic detergents belong to the class of associated colloids.
