What are lyophilic and lyophobic colloids? Which of these sols can be easily coagulated on the addition of small amounts of electrolytes?
Lyophilic colloids: It is made up of two words; ‘Lyo’ meaning liquid and ‘Phillic’ meaning loving, so those colloids which are attracted by the liquid (solvent), are called as lyophilic colloids. These are also called reversible sols. These are quite stable and cannot be easily coagulated. Example are Sols of organic substances like gelatin, gum, starch and proteins
Lyophobic colloids: It is made up of two words; ‘Lyo’ meaning liquid and ‘Phobic’ meaning repelling, so those colloids which are repelled by the liquid ( solvent), are called as lyophobic colloids. These are also called irreversible sols and these are unstable and can be easily coagulated due to lack of protecting layer around charged colloidal particles, they easily form a cluster. Hence, they got easily coagulated on the addition of small amount of electrolyte. Examples are Sols of inorganic substances like Arsenic (As2S3), Iron (Fe(OH)3) and Platinum.
Write the differences between physisorption and chemisorption with respect to the following:
(i) Specificity
(ii) Temperature dependence
(iii) Reversibility and
(iv) Enthalpy change
Define the following terms:
(i) Brownian movement
(ii) Peptization
(iii) Multimolecular colloids
What is meant by coagulation of a colloidal solution? Describe briefly any three methods by which coagulation of lyophobic sols can be carried out.
Write the dispersed phase and dispersion medium of the following colloidal systems:
(i) Smoke (ii) Milk
Define the following terms giving an example of each:
(i) Associated colloids
(ii) Lyophilic sol
(iii) Adsorption
