Extraction of Metals - Result Question 12
####12. The reaction that does not define calcination is
(a) $Fe _2 O _3 \cdot X H _2 O \xrightarrow{\Delta} Fe _2 O _3+X H _2 O$
(2019 Main, 11 Jan II)
(b) $ZnCO _3 \xrightarrow{\Delta} ZnO+CO _2$
(c) $CaCO _3 \cdot MgCO _3 \xrightarrow{\Delta} CaO+MgO+2 CO _2$
(d) $2 Cu _2 S+3 O _2 \xrightarrow{\Delta} 2 Cu _2 O+2 SO _2$
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Solution:
- Calcination is one of the pyrometallurgical process, like roasting by which a concentrated ore gets converted into its oxide.
In calcination, a hydrated carbonate or bicarbonate ore or a hydrated ore is heated at lower temperature (compared to roasting) in absence of air to give its oxide as in options (a), (b) and (c). Here, volatile non-metallic oxides like $H _2 O, CO _2$, are also produced.
Roasting is valid mainly for sulphide ores like option (d), where $SO _2$ gets liberated. In this reaction, calcination cannot be used.
