Question

Assertion: Sulphide ores are concentrated by froth flotation process.
Reason: Pine oil forms emulsions in water.
A.If both assertion and reason are correct and the reason is the correct explanation for the assertion.
B.If both assertion and reason are correct but the reason is not the correct explanation for the assertion.
C.If the assertion is correct but the reason is incorrect.
D.If the assertion is incorrect and the reason is correct.

Answer 1

Hint: To answer this question, you should recall the concept of the froth flotation process. This process is used for mineral beneficiation. In ore/mineral beneficiation, froth flotation is a method by which commercially important minerals are separated from impurities and other minerals by collecting them on the surface of a froth layer.

Complete step by step answer:
- The process of froth flotation is the process of separation of beneficial minerals from a mixture by creating froth on which minerals separate.
- In this method of mineral processing, the ores contain multiple metals such as lead, copper and zinc can be selectively extracted by using froth floatation. The process of froth floatation starts with the step known as comminution process in which the surface area of the ore is increased.
- In this step, the ores are crushed into very fine powder sized particles and mixed with water. The mixture obtained is called Slurry. This pulp is added in the container filled with water and then air jets are forced into it to create bubbles.
- The required mineral is repelled by water and thus gets attached to the air bubbles. As these air bubbles rise to the surface with mineral particles sticking to it, these are called froth. This Froth is separated and further taken for the next process of refining and extraction.
- Froth floatation method is used for the concentration of sulphide ores such as galena \[\left( {PbS} \right),\]zinc blende \[\left( {ZnS} \right)\] and copper pyrites \[(CuFe{S_2})\]. The single most important operation used for the recovery and upgrading of sulphide ore. Only sulphide ores are concentrated by the froth flotation process because pine oil selectively wets the sulphide ore and hence brings it to the froth. The sulphide ores preferably wetted by the oil and the gangue with the water.

Hence, we can conclude that the correct answer to this question is option A.

Note:
You should know about the different chemicals used to maintain uniform quality of froth and optimise the adhesive quality of the minerals: collector, frother, regulator, activator, depressant and pH modifier. An important criterion of separation of minerals by the froth floatation method is that the size of the particles of the ores must be very small equivalent to powder form. This is very important because the heavier and bigger particle would require a greater adhesive force without which they would no longer attach to the froth and settle down in the bottom. Thus separation will not be possible.