Write the principle of the following
(a) Zone refining
(b) Froth floatation process
(c) Chromatography

Explanation

(a) The principle of zone refining is that the impurities in an ingot or ore of metal are more soluble in the melt state when compared to the corresponding solid state of the impurities. In the zone refining process, the impurities are concentrated at one end of the block of metal so that the rest of the block is purified.
(b) Froth floatation process: This method is widely used for the concentration of sulphide ores such as zinc blende (`ZnS`), copper pyrites `(CuFeS_(2))`, galena (`PbS`) etc. It is based upon the principle that the surface of sulphide ores is preferentially wetted by oils become lighter and thus, rise to the surface along with froth while the gangue particles which preferentially wetted by water become heavier and thus, settle down at the bottom of the tank.
(c) Chromatography is based on the principle where molecules in mixture applied onto the surface or into the solid, and fluid stationary phase (stable phase) is separating from each other while moving with the aid of a mobile phase.