(1)2CuFeS2+5O2=2Cu+2FeO+4SO2:n(O2)=15mol(2)O2不足量(缺少0.75mol):2CuFeS2+4O2=Cu2S+3SO2+2FeO:消耗氧气12molCu2S+O2=2Cu+SO2,有2.25mol氧气反应,得到n(Cu)=4.5mol(3)O2过量(多0.75mol):4Cu+O2=2Cu2O,n(Cu)=6-3=3mol