A) Smelting
B) Calcination
C) Annealing
D) Roasting
Correct Answer: D
Solution :
Roasting is the process of heating the ore strongly in the presence of excess of air. The process is usually carried for sulphide ore and the following changes take place. (i) Moisture is removed (ii) The voltatile impurities are removed (iii) Impurities of sulphur, arsenic, phosphorus etc., are removed in form of volatile oxide. \[S+{{O}_{2}}\xrightarrow{{}}S{{O}_{2}}\uparrow \] \[4As+3{{O}_{2}}\xrightarrow{{}}2A{{s}_{2}}{{O}_{3}}\uparrow \] \[{{P}_{4}}+5{{O}_{2}}\xrightarrow{{}}2{{P}_{2}}{{O}_{5}}\uparrow \] (iv) Sulphide ores get oxidised into metal oxides\[2Fes+3{{O}_{2}}\xrightarrow{{}}FeO+2S{{O}_{2}}\]Calcination is the process in which concentrated ore is heated in limited supply of air below its melting point to remove moisture, volatile impurities make the ore porus and convert carbonate ore to oxide ore. Smelting: Reduction of an ore with carbon in the blast furnace is called smelting. Annealing: If steel (or glass) is heated at a temperature below hot and then cooled slowly the process is called annealing.
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