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Questions
Explain:
Zone refining
Outline the principles of refining of metals by the following method:
Zone refining
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Solution
Zone refining: This method is based on the principle that impurities are more soluble in the molten state of metal (the melt) than in the solid state. In the process of zone refining, a circular mobile heater is fixed at one end of a rod of impure metal. As the heater moves, the molten zone of the rod also moves with it. As a result, pure metal crystallizes out of the melt, and the impurities pass onto the adjacent molten zone. This process is repeated several times, which leads to the segregation of impurities at one end of the rod. Then, the end with the impurities is cut off. Silicon, boron, gallium, indium, etc. can be purified by this process.
RELATED QUESTIONS
Name the common elements present in the anode mud in electrolytic refining of copper. Why are they so present?
Outline the principles behind the refining of metals by the following methods:
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Vapour-phase refining
Name the method of refining which is Used to obtain semiconductor of high purity.
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In which of the following method of purification, metal is converted to its volatile compound which is decomposed to give pure metal?
(i) Heating with stream of carbon monoxide.
(ii) Heating with iodine.
(iii) Liquation.
(iv) Distillation.
Which method is used for refining Zr and Ti? Explain with equation.
How are metals used as semiconductors refined? What is the principle of the method used?
Give two requirements for vapour phase refining.
Match the items of Column I with the items of Column II and assign the correct code:
| Column I | Column II |
| (A) Coloured bands | (1) Zone refining |
| (B) Impure metal to volatile complex | (2) Fractional distillation |
| (C) Purification of Ge and Si | (3) Mond Process |
| (D) Purification of mercury | (4) Chromatography |
| (5) Liquation |
Assertion: Nickel can be purified by Mond process.
Reason: \[\ce{Ni(CO)4}\] is a volatile compound which decomposes at 460 K to give pure Ni.
Assertion: Zone refining method is very useful for producing semiconductors.
Reason: Semiconductors are of high purity.
Assertion: Hydrometallurgy involves dissolving the ore in a suitable reagent followed by precipitation by a more electropositive metal.
Reason: Copper is extracted by hydrometallurgy.
Electrolytic reduction method is used for the extraction of ______.
Describe a method for refining nickel.
Describe a method for refining nickel.
Describe a method for refining nickel.
Describe a method for refining nickel.
