Auto Reduction of Copper Sulfide with Copper Reagents

To determine which reagent(s) produce metallic copper upon heating with cuprous sulfide ($\text{Cu}_2\text{S}$), we analyze the chemistry of the self-reduction (auto-reduction) process involved in copper metallurgy:

1. Reaction with $\text{Cu}_2\text{O}$ (Option C): In the extraction of copper, part of the cuprous sulfide ($\text{Cu}_2\text{S}$) is oxidized during roasting to cuprous oxide ($\text{Cu}_2\text{O}$). Upon further heating in the absence of air (Bessemer converter), auto-reduction takes place to yield metallic copper: $\text{Cu}_2\text{S} + 2\text{Cu}_2\text{O} \xrightarrow{\Delta} 6\text{Cu} + \text{SO}_2\uparrow$

2. Reaction with $\text{CuO}$ (Option B): Similarly, cupric oxide ($\text{CuO}$) acts as an oxidizing agent and reacts with $\text{Cu}_2\text{S}$ at elevated temperatures to yield metallic copper: $\text{Cu}_2\text{S} + 2\text{CuO} \xrightarrow{\Delta} 4\text{Cu} + \text{SO}_2\uparrow$

3. Reaction with $\text{CuSO}_4$ (Option D): During the roasting of copper sulfide ores, some copper(II) sulfate ($\text{CuSO}_4$) is also formed. When heated with the remaining $\text{Cu}_2\text{S}$, it undergoes reduction to produce metallic copper: $\text{Cu}_2\text{S} + \text{CuSO}_4 \xrightarrow{\Delta} 3\text{Cu} + 2\text{SO}_2\uparrow$

4. Reaction with $\text{CuFeS}_2$ (Option A): Copper pyrites ($\text{CuFeS}_2$) is itself a sulfide ore and lacks the necessary oxidizing oxygen species required to oxidize the sulfide in $\text{Cu}_2\text{S}$ to $\text{SO}_2$ and liberate metallic copper. Hence, no metallic copper is produced by heating $\text{Cu}_2\text{S}$ with $\text{CuFeS}_2$.

Therefore, the reagents that produce metallic copper are $\text{CuO}$, $\text{Cu}_2\text{O}$, and $\text{CuSO}_4$.

Correct Options: (B), (C), and (D)