Question

Sulphide ores of metals are usually concentrated by the froth floatation process. Which one of the following Sulphide Ores offers an exception and is concentrated by chemical leaching?
A: Argentite
B: Galena
C: Copper pyrite
D: Sphalerite

Answer 1

Hint: Ores are naturally occurring solid material from which a metal is extracted profitably. Sulphide ores are the source of various precious metals and metals used in industries.

Complete step by step solution:
Froth flotation is a process which is used for selectively separating hydrophobic materials from hydrophilic material. Hydrophilic means water loving which can be easily dissolved in water and hydrophobic means water hating which can not be dissolved in water easily. This is used in mineral processing, paper recycling and waste-water treatment industries. It is the most used process for separating metal from its sulphide ore. This method is based on the principle of the difference in the wetting properties of the ore and the gangue particles with the water and oil. Gangue is the impurity which is found in ores. The sulphide ores preferably wetted by the oil and the gangue with the water. Oil being lighter will float on water and sulphide ore will also float along with oil and impurities will settle down with water. So, ore can be easily extracted from the floating layer.
Leaching is the process of extracting substance from solid material which is dissolved in liquid. Processes involved in leaching are contact, separation and extraction.
In the froth floatation process some amount of ore also settles down with impurities. So metals which are expensive are not extracted with a froth floatation process as it will cause loss of meta. Among given options Argentite is ore of silver which is an expensive metal. So it is not extracted with a froth floatation process to avoid loss.
Hence answer to this question is option A i.e., Argentite.

Note: You can remember the froth floatation process by its name. This name clearly suggests that something is floating on the surface of liquid.Since Froth means a mass of small bubbles in liquid caused by agitation.