Products of Partial Roasting of Chalcopyrite

Chalcopyrite ($\text{CuFeS}_2$) is an ore containing copper and iron sulfides. When chalcopyrite is subjected to partial roasting in a limited supply of air (reverberatory furnace), the following step-by-step chemical transformations occur:

1. Thermal Oxidation/Decomposition of Chalcopyrite:
   Chalcopyrite initially reacts with oxygen to yield cuprous sulfide ($\text{Cu}_2\text{S}$), ferrous sulfide ($\text{FeS}$), and sulfur dioxide ($\text{SO}_2$):
   $2\text{CuFeS}_2 + \text{O}_2 \xrightarrow{\Delta} \text{Cu}_2\text{S} + 2\text{FeS} + \text{SO}_2 \uparrow$

2. Preferential Oxidation of Iron Sulfide:
   Iron has a higher affinity for oxygen than copper. Therefore, ferrous sulfide ($\text{FeS}$) is preferentially oxidized to ferrous oxide ($\text{FeO}$):
   $2\text{FeS} + 3\text{O}_2 \xrightarrow{\Delta} 2\text{FeO} + 2\text{SO}_2 \uparrow$

3. Re-conversion of any Cuprous Oxide Formed:
   If any cuprous oxide ($\text{Cu}_2\text{O}$) is formed during partial roasting, it immediately reacts with the remaining $\text{FeS}$ due to the greater affinity of iron for oxygen:
   $\text{Cu}_2\text{O} + \text{FeS} \longrightarrow \text{Cu}_2\text{S} + \text{FeO}$

Thus, the main products formed upon partial roasting of chalcopyrite are $\text{Cu}_2\text{S}$ and $\text{FeO}$.

Correct Answer: A