(a) Name the method of refining which is (i) used to obtain semiconductor of high purity (ii) used to obtain low boiling metal. (b) Write chemical reactions taking place in the extraction of copper from `Cu_(2)S`.

(a) Name the method of refining which is (i) used to obtain semiconduc

1.	(a) Name the method of refining which is (i) used to obtain semiconductor of high purity (ii) used to obtain low boiling metal. (b) Write chemical reactions taking place in the extraction of copper from `Cu_(2)S`.
Answer» (i) Zone refining. (ii) Distillation. (b) It is first heated in air to get copper oxide. `2Cu_(2)S+3O_(2)to2Cu_(2)O+2SO_(2)` It is then reduced to the corresponding copper metal by the following reaction `2Cu_(2)O+Cu_(2)Sto6Cu+SO_(2)`

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(i) Arrange the following compounds in an increasing order of basic strength : `C_(6)H_(5)NH_(2), C_(6)H_(5)N(CN_(3))_(2), (C_(2)H_(5))_(2)NH and CH_(3)NH_(2)` (ii) Arrange the following compounds in a decreasing order of `pK_(b)` values: `C_(2)H_(5)NH_(2), C_(6)H_(5)NHCH_(3), (C_(2)H_(5))_(2) NH and C_(6)H_(5)NH_(2)`
Rerrange the following in an increasing order of their basic strengths: `C_(6)H_(5)NH_(2),C_(6)H_(5)N(CH_(3))_(2),(C_(6)H_(5))_(2)` NH and `CH_(3)NH_(2)`.
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(a) Name the method of refining which is (i) used to obtain semiconductor of high purity (ii) used to obtain low boiling metal. (b) Write chemical reactions taking place in the extraction of copper from `Cu_(2)S`.

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