\(n_{FeSO_4}=0.2\cdot1=0.2\left(mol\right)\)
\(2A+nFeSO_4\rightarrow A_2\left(SO_4\right)_n+nFe\)
\(\dfrac{0.4}{n}.........................0.2\)
\(m_{tăng}=m_{Fe}-m_A=0.2\cdot56-\dfrac{0.4}{n}\cdot A=6.4\left(g\right)\)
\(\Rightarrow\dfrac{0.4A}{n}=4.8\)
\(\Rightarrow A=12n\)
\(BL:n=2\Rightarrow A=24\)
\(A:Magie\)