Question

Sulphide ores of metals are usually concentrated by Froth Floatation process. Which one of the following sulphide ores offer and exception and is concentrated by chemical leaching?
a.) Sphalerite
b.) Argentite
c.) Galena
d.) Copper pyrite

Answer 1

To answer this question, let us first recall what the froth floatation process entails and in which cases is it chosen as a method of concentration.

Complete step by step solution:

We should know that in ore or mineral concentration, froth flotation is a method by which commercially important minerals are separated from their impurities and other minerals by collecting them on the top surface of a froth layer.
Let us now take a look at the process of froth floatation briefly:

First of all, the ores are crushed into very fine powder sized particles which are then mixed with water. This is actually a comminution process in which the surface area of the ore is increased.
A collector which acts as a surfactant chemical is then added to the slurry. This enhances the hydrophobic nature of the mineral.
The slurry is then converted to pulp and this pulp is added in the container filled with water and then air jets are forced into it to produce bubbles. The required mineral is repelled by water and thus gets attached to the air bubbles.
The basic principle of separation in the process of Froth Flotation is the difference in the wetting ability of the ore and the remaining impurities. Some are hydrophobic while others are hydrophilic.

In the options provided here, Sphalerite is separated by chemical leaching. This involves the ore dissolving in a chemical solution.
Hence, the correct answer is Option (A) Sphalerite.

Note: We should remember that Ores which contain multiple metals such as lead, copper and zinc can be selectively extracted by using froth floatation. Hence, sulphide ores are mostly separated by froth floatation.