\(1-C.n_{CuO}=\dfrac{240}{80}=3\left(mol\right)\\ 2-C.Photpho\left(P\right)vìđâylàphikim\\ 3-C.FeCl_3\\ 4-C.4P+5O_2-^{t^o}\rightarrow2P_2O_5\\ n_P=\dfrac{124}{31}=4\left(mol\right)\\ n_{P_2O_5}=\dfrac{1}{2}n_P=2\left(mol\right)\\ \Rightarrow m_{P_2O_5}=2.142=284\left(g\right)\)