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Outline the principles of refining metals by the following methods : (i) Zone refining (ii) Electrolytic refining (iii) Vapour phase refining |
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Answer» Solution :(i) Zone REFINING : This process is based upon the principle that IMPURITIES are more soluble in the molten state of the metal than in the solid form. (II) Electrolytic refining : It is USED for less reactive metals like Cu, Ag, Al, etc. In it, anode is made by impure metal and a thin strip of pure metal acts as cathode. On passing electricity, metal dissolves form anode and pure metal gets deposited at cathode. At anod `MrarrM^(n+)+n e^(-)` `{:("Impure"),("Metal"):}` At cathode `M^(n+)+n e^(-)rarrM` Pure Metal Impurities settle down below anode in the form of anode mud. (III) Vapour phase refining : This method is based upon the following facts : (a) Metal to be refined should form a volatile compound, while impurities do not. (b) Volatile compound should be easily decomposable so that pure metal can be recovered easily. |
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