Copper was first heated up in a crucible with sulfur to form copper sulfide. So if there is enough oxygen present to form copper (II) oxide, will CuS break apart to form copper oxide in the present of oxygen as well as sulfur oxide? or will it not react at all because all the copper had already reacted with sulfur?
However if all the copper did not reacted with sulfur, then oxygen should be able to react with the copper to form copper oxide right?