\(n_{N_2}=a,n_{H_2}=b\\ M_A=\dfrac{28a+2b}{a+b}=7,2\\ a=4b\\ PT:\dfrac{1}{2}N_2+\dfrac{3}{2}H_2-Fe,t^{^0}->NH_3\\ CuO+H_2-t^{^0}->Cu+H_2O\\ n_{Cu}=n_{H_2dư}=\dfrac{32,64}{64}=0,51mol\\ n_{H_2pư}=b-0,51\left(mol\right)\\ H=\dfrac{b-0,51}{b}=0,2\\ b=0,6375\\ a=2,55\\ V_A=22,4\left(0,6375+2,55\right)=71,4L\)