Question

Colloidal solution can be purified by:
(A) Dialysis
(B) Electrodialysis
(C) Electrophoresis
(D) Ultrafiltration

Answer 1

Hint: In dialysis, by phenomenon of diffusion, ions are removed from solution through semi permeable membranes. In electrodialysis, the dialysis of colloidal solution is carried under the effect of electric field. In ultrafiltration, by electrolysis, particles of solution are removed from the liquid medium using ultrafilter.

Complete step by step solution:
For purification of colloidal solutions, following methods are common:
In Dialysis, particles of colloid are separated from crystalloid by phenomenon of diffusion via semi permeable membranes.It is principle is based upon the fact that colloidal particles cannot pass through a parchment or cellophane membrane while the ions of the electrolyte can pass through it.There is slow diffusion of impurities while pure colloidal solution is left behind.
Electrodialysis-.In the process of electrodialysis, The dialysis is carried out by under the influence of electric fields, to increase the process of purification.
 Ultra – filtration:- As pores are larger than the size of sol particles, Sol particles directly pass through ordinary filter paper. By soaking the filter paper in a solution of gelatin of collodion ,the pores of the ordinary filter paper are made smaller and which is hardened by soaking in formaldehyde,colloidal particles are retained by the treated filter paper and true solution particles are allowed to escape. Such treated filter paper is known as ultra - filter and ultra – filtration utilizes ultra filter papers to separate particles of colloids.
The existence of charge on colloidal particles is confirmed using electrophoresis.

So, the correct option is (A) Dialysis, (B) Electrodialysis and (D) ultrafiltration.

Note: To avoid accumulation of crystalloid which may lead to back diffusion , distilled water is frequently changed.Dialysis can be used for purifying the ferric hydroxide sol.Electrodialysis finds its application in artificial kidney machines which is used in purifying blood of kidneys. Artificial kidney machines work on the basis of electrodialysis.