Question

Which of the following fluxes is used to remove acidic impurities in metallurgical processes?
(A) Silica
(B) Limestone
(C) Sodium chloride
(D) Sodium carbonate

Answer 1

Hint: The flux is a substance that is used to remove the impurities present in the ore. The various materials that can be used as fluxes are silica, lime, dolomite, fluorite, and borax. We know that there are two types of flux: acidic flux and basic flux. The acidic flux combines with basic impurity, and the basic flux combines with acidic impurity to form slag.

Complete Step by Step Answer:
We are given that there is an acidic impurity present in the ore. We know that to remove an acidic impurity, a basic flux is required. As a result, it will form slag. The slag thus formed is a mixture of metal oxide and silicon dioxide. It occurs as a molten liquid. After cooling, the slag solidifies.

Only the formation of the slag, which includes solid impurities and will be settled down in the process of purifying the metal in the metallurgical process, results from the presence of the flux. Among the given options, limestone is the only basic flux. Hence, limestone is used to remove acidic impurities in metallurgical processes.
Correct Option: (B) Limestone.

Note: Flux often has a dual purpose in facilitating the wetting of molten metal by dissolving the oxides already present on the metal surface and serving as an oxygen barrier by covering the hot surface to prevent oxidation.