CBSE Class 10 Science 2019 · Paper 31/2/3 · Question 4

Metal of medium reactivity: zinc (iron or lead are also accepted). Three main steps in extracting zinc from its sulphide ore, zinc blende ($\text{ZnS}$): (i) Concentration (enrichment) of the ore: the gangue is removed, for example by froth flotation. (ii) Roasting: the concentrated ore is heated strongly in excess air, which converts the sulphide into the oxide: $2\text{ZnS}+3{\text{O}}_2\stackrel{\text{heat}}{\to }2\text{ZnO}+2{\text{SO}}_2$. (iii) Reduction: the oxide is heated with carbon (coke) to give the metal: $\text{ZnO}+\text{C}\stackrel{\text{heat}}{\to }\text{Zn}+\text{CO}$.