Short Answer TypeWrite the dispersed phase and dispersion medium of the following colloidal systems:
(i) Smoke (ii) Milk
What are lyophilic and lyophobic colloids? Which of these sols can be easily coagulated on the addition of small amounts of electrolytes?
Write the differences between physisorption and chemisorption with respect to the following:
(i) Specificity
(ii) Temperature dependence
(iii) Reversibility and
(iv) Enthalpy change
What is meant by coagulation of a colloidal solution? Describe briefly any three methods by which coagulation of lyophobic sols can be carried out.
Define each of the following terms:
(i) Micelles
(ii)Peptization
(iii)Desorption
(i) A micelle is an aggregate of surfactant molecules dispersed in a liquid. A micelle in aqueous solution forms an aggregate such that the hydrophilic "head" regions are in contact with the surrounding solvent and the hydrophobic tail regions are in the center of micelle.
(ii) Peptization is the process of conversion of a precipitate into a colloidal sol by shaking it with the dispersion medium in the presence of an electrolyte. The electrolyte used in this reaction is known as a peptizing agent.
(iii) Desorption is the process of removing an adsorbed substance from the surface through which it was adsorbed.
Define the following terms:
(i) Brownian movement
(ii) Peptization
(iii) Multimolecular colloids
Define the following terms giving an example of each:
(i) Associated colloids
(ii) Lyophilic sol
(iii) Adsorption
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