alleryStart learning →Which reaction represents calcination?
A$2Zn + O_2 \rightarrow 2ZnO$
B$MgCO_3 \rightarrow MgO + CO_2$
C$2ZnS + 3O_2 \rightarrow 2ZnO + 2SO_2$
D$4Au + 8CN^- + O_2 + 2H_2O \rightarrow 4[Au(CN)_2]^- + 4OH^-$
Answer & Solution
Correct answer: B. $MgCO_3 \rightarrow MgO + CO_2$
1. Calcination is strong heating of an ore in the **absence (or limited supply) of air**, driving off $CO_2$ or water of hydration.
2. $MgCO_3 \rightarrow MgO + CO_2$ is decomposition of a carbonate on heating — a calcination.
3. The $ZnS$ reaction is roasting (needs $O_2$); the gold reaction is cyanide leaching.
_Source: Samacheer Kalvi Class 12 Chemistry Vol.1, Unit 1 'Metallurgy', §1.3.1 / Evaluation Q.3_
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