Question

Define the following term: Protective Colloid.

Answer 1

Hint :We know that the nature of lyophilic colloids against lyophobic colloids. Presence of lyophilic colloids is beneficial for lyophobic colloids. Whereas, lyophobic colloids are solvent hating colloids. In lyophobic colloids, the dispersed phase does not have any attraction for the dispersion medium.

Complete Step By Step Answer:
We should know that a protective colloid is a lyophilic colloid that when present in small quantities keeps lyophobic colloids from precipitating under the coagulating action of electrolytes. We should know that lyophilic sols are more stable than lyophobic sols. It is due to the fact that lyophilic colloids are extensively solvated, which means colloidal particles are covered by a sheath of the liquid in which they are dispersed.
It is interesting to know that lyophilic colloids have a unique property of protecting lyophobic colloids. When a lyophilic sol is added to the lyophobic sol, the lyophilic particles form a layer around lyophobic particles and thus protect the latter from electrolytes. Lyophilic colloids used for this purpose are called protective colloids. Coagulation of gold sol is indicated by colour change from red to blue/purple when particle size just increases.
Protective colloid is lyophilic colloid when present in small quantities keeps lyophobic colloids from precipitating under the coagulating action of electrolytes.

Note :
Remember that about lyophilic colloids. They are solvent loving colloids. In lyophilic colloids, the dispersed phase shows a positive affinity for the dispersion medium (solvent). The high affinity of dispersed particles with the dispersed medium is due to the formation of a large number of hydrogen bonds.