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Each of the following statements is true...

Each of the following statements is true only under some specific conditions. Write the condition for each sub-equation in not more than two sentences.
(i) Metals can be recovered from their ores by chemical methods.
(ii) High purity metals can be obtained by zone refining method.

Text Solution

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(i) Many metals occur in nature as oxides, carbonates, sulphides, which can be calcined or roasted. Then, they can further treated chemically to get the metal.
(ii) Elements such as `Si,Ge,Ga` etc., which are used as semiconductors, are refined by zone refining method. Highly pure metals are obtained. The method is based on the difference in solublility of impurities on molten and solid state of the metal. A movable heater is fitted around a rod of the impure metal. The heater is slowly mogved across the rod. The metal melts at the point of heating, and as the heater moves on from one end of the rod to the other end, the pure metal crystallises, while the impurities pass on to the adjacent molten zonc.
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