A) smelting
B) roasting
C) calcination
D) dressing
Correct Answer: C
Solution :
Calcination is a process in which the ore is heated strongly in the absence of air. It removes volatile impurities like \[C{{O}_{2}},S{{O}_{2}}\], moisture from the ore. It removes water from hydrated oxide ore. \[\underset{\begin{smallmatrix} bauxite \\ \left( hydrated\text{ }alumina \right) \end{smallmatrix}}{\mathop{A{{l}_{2}}{{O}_{3}}.\,2{{H}_{2}}O}}\,\,d\,\,\xrightarrow{calcmation}\underset{\begin{smallmatrix} anhy. \\ aluminium \\ oxide \end{smallmatrix}}{\mathop{A{{l}_{2}}{{O}_{3}}}}\,+2{{H}_{2}}O\] It also removes \[C{{O}_{2}}\] from a carbonate ore. \[\underset{limestone}{\mathop{C{{O}_{2}}}}\,\xrightarrow{Calcination}CaO+C{{O}_{2}}\] Therefore, the process of converting hydrated alumina into anhydrous alumina is called calcination. Note - Roasting is a process in which the sulphide ore is heated strongly in the presence of air. In roasting the ore is converted into its oxide. Smelting is a process in which the oxide ore in the fused state is reduced by carbon to the free metal. Dressing : There are many impurities like soil, stones, clay, etc., present in the ore. These impurities are called ganuge. The removal of these impurities from ore is called dressing.
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