In the extraction process of copper, the product obtained after carrying out the reactions

(i) $$2 \mathrm{Cu}_{2} \mathrm{~S}+3 \mathrm{O}_{2} \rightarrow 2 \mathrm{Cu}_{2} \mathrm{O}+2 \mathrm{SO}_{2}$$

(ii) $$2 \mathrm{Cu}_{2} \mathrm{O}+\mathrm{Cu}_{2} \mathrm{~S} \rightarrow 6 \mathrm{Cu}+\mathrm{SO}_{2}$$ is called

The sequence of reactions stated here is part of the copper extraction process, specifically the smelting and conversion stages. Initially, copper sulfide (Cu$_2$S) reacts with oxygen (O$_2$) to form copper(I) oxide (Cu$_2$O) and sulfur dioxide (SO$_2$), according to the equation : <br/><br/>$$2 \mathrm{Cu}_2 \mathrm{S} + 3 \mathrm{O}_2 \rightarrow 2 \mathrm{Cu}_2 \mathrm{O} + 2 \mathrm{SO}_2.$$ <br/><br/>Subsequently, the resulting copper(I) oxide then reacts with remaining copper sulfide to yield copper (Cu) and additional sulfur dioxide : <br/><br/>$$2 \mathrm{Cu}_2 \mathrm{O} + \mathrm{Cu}_2 \mathrm{S} \rightarrow 6 \mathrm{Cu} + \mathrm{SO}_2.$$ <br/><br/>The output of this process, which contains about 98-99% copper, is known as "blister copper". This name derives from the blister-like appearance of the copper surface, which results from the release of sulfur dioxide gas during the reaction.