a) Zn + H2SO4 --> ZnSO4 + H2
Fe + H2SO4 --> FeSO4 + H2
b) Gọi số mol Zn và Fe là a,b (mol)
Chất rắn không tan là Cu
=> \(m_{Zn}+m_{Fe}=21,6-3=18,6\left(g\right)\)
=> 65a + 56b = 18,6 (g) (1)
\(n_{H_2}=\frac{6,72}{22,4}=0,3\left(mol\right)\)
PTHH: \(Zn+H_2SO_4\rightarrow ZnSO_4+H_2\uparrow\)
_______a--------------------------------> a___(mol)
\(Fe+H_2SO_4\rightarrow FeSO_4+H_2\uparrow\)
b---------------------------------> b___(mol)
=> a+b=0,3 (2)
(1)(2)=> \(\left\{{}\begin{matrix}a=0,2\left(mol\right)\\b=0,1\left(mol\right)\end{matrix}\right.\)
\(=>\left\{{}\begin{matrix}\%m_{Zn}=\frac{0,2.65}{21,6}.100\%=60,18\%\\\%m_{Fe}=\frac{0,1.56}{21,6}.100\%=25,93\%\\\%m_{Cu}=\frac{3}{21,6}.100\%=13,89\%\end{matrix}\right.\)
