Some of the important applications of colloids are given below. Identify and justify the properties, of colloids responsible for the applications. i.Purification of water

Explanation

i. Coagulation using. alums. The Al.t ions present in the. atum precipitate colloidal dirt particles in water.
ii. Soap.forms colloids (micelle) and emulsifies the grease. The cleaning action of soap is based on its tendency to form micelles. Dirt sticks to an oily or greasy, layer on the fabrịc. When soap is added to dirty clothes in water, the micelles remain suspended in water entrapping the dirt particles by attaching the inydrophobic end of the soap molecule to the oily layer and the polar end to water. This reduces the interfacial tension between oil and water andे the oily dirt particles get displaced in water forming an emulsion. Thus the cloth gets cleaned.
iii. Sewage consists of negatively charged sols which can.be removed by creating an elec.tric field in the sewage tank. The particles migrate towards oppositely charged electrode. lose their charge and get coagulated: