Question

Which of the following sol is not prepared using Bredig’s arc method?
A. Silver sol
B. Copper sol
C. Gold sol
D. Platinum sol

Answer 1

A sol is a colloid formed from small particles in which any solid is the dispersed phase, while a liquid is the dispersed medium. Bredig’s arc method is used in the preparation of colloids, which is also called as electrical disintegration method to form colloids. It involves vaporization, and condensation.

Complete answer:
Sols are colloids which are termed as substances that have a dispersed phase, and a dispersed medium, in which the particles of the dispersed phase are held. It is a heterogeneous system and consists of fine particles as dispersed phases.
Bredig’s arc method is the process used for the preparation of colloids. This method involves dispersion as well as condensation. It has an electric arc struck between the electrodes of the metal immersed in the dispersion medium. A high amount of heat is produced that vaporizes the metal, which then condenses to produce a colloidal solution, and hence sols are prepared.
This method is used to prepare the sol of silver platinum and gold as these metals do not become reactive at high temperature, while copper sol is not prepared using this method.

Hence, copper sol is not formed from Bredig’s arc method, so option B is correct.

Note:
Other methods through which copper sol may be produced are the chemical methods. These involve double decomposition, oxidation and reduction, or hydrolysis. One such reaction is subjecting copper chloride to high temperature in presence of water.