CBSE Class 10 Science 2019 · Paper 31/5/1 · Question 15

The ore is a carbonate ore: a carbonate gives off carbon dioxide with dilute hydrochloric acid, seen as brisk effervescence (${\text{ZnCO}}_3+2\text{HCl}\to {\text{ZnCl}}_2+{\text{H}}_2\text{O}+{\text{CO}}_2$). Example: zinc carbonate, ${\text{ZnCO}}_3$ (calamine). Steps to obtain the metal from the enriched ore: (i) Calcination: the ore is heated strongly in a limited supply of air, which converts it into the metal oxide: ${\text{ZnCO}}_3\stackrel{\text{heat}}{\to }\text{ZnO}+{\text{CO}}_2$. (ii) Reduction: the metal oxide is heated with carbon (coke), which reduces it to the metal: $\text{ZnO}+\text{C}\to \text{Zn}+\text{CO}$.