Question

Cataphoresis is the process used for the coagulation of colloids. It can be used for:
(A) Colloids having positive charge
(B) Colloids having negative charge
(C) Lyophilic colloids
(D) All of the above

Answer 1

To answer this question, you must recall the methods of separation of colloidal solutions based on the types of relation between the colloidal particles and the solvent. Colloids are a type of mixture of solute particles distributed evenly throughout another substance or the solvent.

Complete answer:
A colloidal mixture is a mixture in which a substance having dispersed soluble or insoluble particles are suspended in another substance. These dispersed particles have a size small enough to not be seen by the naked eye and their diameter ranges from 1 to 1000 nanometers.
Electrophoresis is the process of subjecting a colloidal solution to a uniform electric field that causes the motion of the dispersed phase relative to the dispersion medium. Positively charged particles are known as cations. Thus, the electrophoresis of the positively charged colloid particles is known as cataphoresis. Colloidal solutions have an important characteristic property that all the suspended particles carry a certain charge be it positive or negative. The repulsion between these charges prevents the particles from aggregating and settling down under the action of gravity.
Cataphoresis causes the accumulation of the charged particles and thus can be used for the coagulation of both positively and negatively charged colloids. Lyophilic colloids are those colloids which have a strong affinity for the particles of the dispersion medium. Cataphoresis can also be used to coagulate these colloids.
The correct answer is D.

Note:
The size of the particles in a colloid is bigger than that in a true solution but less than that in a suspension. We know that there are three states of matter, namely solids, liquids and gases. A colloidal solution can be prepared by the combination of any of the three states.