What are lyophilic and lyophobic sols? Give one example of each type. Why are hydrophobic sols easily coagulated ?
Explanation Lyophilic Sols: Lyophilic Solids can be prepared by direct mixing of dispersed phase into dispersion medium. They are stable and cannot be easily coagulated. They are also reversible sols i.e. if dispersion medium is separated from dispersed phase say by evaporation, sol can be prepared simply by remixing them with each other. For example, gum, gelatine, starch, natural rubber etc. Lyophobic Sols: Lyophobic Sols can be prepared by using special methods only. They are less stable than lyophilic sols and can be coagulated easily. They are irreversible sols i.e. if dispersion medium is separated from dispersed phase, sol can’t be prepared simply by remixing them with each other so they need some stabilizing agent. For example, metal sols, metal sulphide sols etc. There are two factors which determine the stability of hydrophobic sols. They are: 1. Solvation of a colloidal particle 2. Presence of charge The removal of charge from colloids leads to precipitation as the particles present in them comes closer forming aggregates i.e. they will coagulate and settle down. So, if solvation and charge removed then colloid gets coagulated. Final Answer Lyophilic Solids can be prepared by direct mixing of dispersed phase into dispersion medium. Lyophobic Sols can be prepared by using special methods only and can be coagulated easily Hydrophobic sols are easily coagulated due to the loss of stability caused by the removal of charge from colloids.
