Question

Bredig’s arc method involves:
A.Dispersion
B.Condensation
C.Peptization
D.Dispersion and Condensation both

Answer 1

Hint:Bredig’s arc method is used for preparing colloidal solutions of metals for instance, gold, silver or platinum. It is a chemical method and involves both dispersion and condensation during the process.

Complete step by step answer:
We will now look into Bredig’s arc method in a more detailed manner.
-Bredig’s arc method is a chemical method and is used to prepare colloidal solutions of metals such as gold, silver or platinum.
-During the whole process we firstly have dispersion and the condensation. So the Bredig’s arc method involves both condensation and dispersion.
-Let us now look into how this whole process works: During the process we have two metal rods made up of the metal of which we want to make a colloidal solution. Both the rods are connected to the opposite terminals of a powerful battery.
-An arc is then made to strike between the electrodes, under the surface of water which contains some stabilizing agent, for instance, potassium hydroxide.
-The intense heat produced due to the arc vaporises the metal (known as dispersion). This metal then condenses under ice cold water (known as condensation), for the condensation the whole apparatus is kept in an ice bath.
-This is why the method involves both dispersion and condensation.

Hence, option D is the correct answer.



Note:
As you notice we have used some stabilizing agents during the process of preparing colloidal solutions.
The role of this stabilizing agent is, as the name suggests, to stabilise the colloidal solution formed. In the absence of it the metal sol formed will aggregate and settle down and hence our purpose of making a colloidal solution will not be fulfilled.