Gọi a, b, b là mol Fe, Mg, Cu trong 25,6g X
\(\Rightarrow56a+24b+64b=25,6\left(1\right)\)
Gọi ka, kb, kb là mol Fe, Mg, Cu trong 1 mol X (k > 0)
\(\Rightarrow k\left(a+b+c\right)=1\left(+\right)\)
\(n_{O2}=0,6\left(mol\right)\)
\(3Fe+2O_2\underrightarrow{^{to}}Fe_3O_4\)
\(2Mg+O_2\underrightarrow{^{to}}2MgO\)
\(2Cu+O_2\underrightarrow{^{to}}2CuO\)
\(\Rightarrow k.\left(\frac{2a}{3}+0,5b+0,5b\right)=0,6\left(++\right)\)
Từ (+)(++) \(\Rightarrow k=\frac{1}{a+b+b}=\frac{0,6}{\frac{2a}{3}+0,5b+0,5b}\)
\(\Rightarrow0,6\left(a+2b\right)=\frac{2a}{3}+b\)
\(\Rightarrow\frac{-a}{15}+0,2b=0\left(2\right)\)
Từ (1)(2) \(\Rightarrow\left\{{}\begin{matrix}a=0,3\\b=0,1\end{matrix}\right.\)
\(m_{Fe}=0,3.56=16,8\left(g\right)\)
\(m_{Mg}=0,1.24=2,4\left(g\right)\)
\(m_{Cu}=0,1.64=6,4\left(g\right)\)