Question

Which of the following is not an example of coagulation?
(A) Creaming of milk
(B) Purification of water by alum
(C) Rubber plating and chrome tanning
(D) Formation of delta at the river banks

Answer 1

Hint : The process which is used to neutralize charges and form a gelatinous mass to trap particles is known as coagulation. Coagulation is the phenomenon of the precipitation of a colloidal solution by adding excess of an electrolyte.

Complete Step By Step Answer:
Colloidal particles have some charge on their surfaces. This charge makes the colloidal solution stable. The electrostatic force of repulsion between similarly charged particles will prevent them from coming closer to form bigger particles. When the charge is removed, the repulsion will stop. The particles come closer and their size increases which results in precipitation. Alum acts as a coagulant for water purification processes. A coagulant binds small particles suspended in raw impure water into larger particles which can be removed by filtration and settling. Creaming of milk is not an example of coagulation. Coagulation can be described as the process of liquid converting to solid or semi-solid state. Rubber plating and chrome tanning are examples of coagulation. The formation of delta at the river banks is an example of coagulation.
Therefore, option A is the correct answer.

Note :
Coagulation plays a major role in several wastewater treatment operations. The most common examples are phosphorus removal and overloaded wastewater treatment plants. Coagulation is synonymous with flocculation. Coagulation is a process of addition of a coagulant to destabilize a stabilized charged particle whereas flocculation is a mixing technique which promotes agglomeration and assists in the settling of particles.