Observe the figure and answer the questions :[Figure of froth flotation: a tank containing water and pine oil, with an agitator at the bottom and air supply through a pipe; bubbles rise through the mixture carrying “Froth” with “Concentrated sulphide…

Answer: (a) Froth floatation method; (b) concentration of sulphide ores; (c) the hydrophobic property of the ore particles and the hydrophilic property of the gangue particles; (d) to mix the ore, water and pine oil and produce froth; (e) zinc blende (ZnS).

(a) The method shown is the froth floatation method.

(b) It is used for the concentration of ores, especially sulphide ores — the gangue is separated from the powdered ore before extraction of the metal.

(c) The method is based on two opposite properties of the particles:

• Hydrophobic property: the particles of metal sulphides are hydrophobic, so they get wetted mainly with oil and float with the froth.
• Hydrophilic property: the gangue particles are hydrophilic, so they get wetted with water and settle down at the bottom.

(d) The agitator rotates rapidly and mixes the powdered ore, water and pine oil thoroughly; together with the air blown in, it produces froth (foam). The ore particles wetted by oil stick to the bubbles and rise with the froth, which is collected from the top.

(e) Zinc blende (ZnS). (Copper pyrites, CuFeS₂, is also concentrated by this method.)